| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/jpeg-decoder-0.1.22/src/idct.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>idct.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../jpeg_decoder/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../jpeg_decoder/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="comment">// Malicious JPEG files can cause operations in the idct to overflow. |
| // One example is tests/crashtest/images/imagetestsuite/b0b8914cc5f7a6eff409f16d8cc236c5.jpg |
| // That's why wrapping operators are needed. |
| </span><span class="kw">use </span><span class="kw">crate</span>::parser::Dimensions; |
| <span class="kw">use </span>std::{convert::TryFrom, num::Wrapping}; |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>choose_idct_size(full_size: Dimensions, requested_size: Dimensions) -> usize { |
| <span class="kw">fn </span>scaled(len: u16, scale: usize) -> u16 { ((len <span class="kw">as </span>u32 * scale <span class="kw">as </span>u32 - <span class="number">1</span>) / <span class="number">8 </span>+ <span class="number">1</span>) <span class="kw">as </span>u16 } |
| |
| <span class="kw">for </span><span class="kw-2">&</span>scale <span class="kw">in </span><span class="kw-2">&</span>[<span class="number">1</span>, <span class="number">2</span>, <span class="number">4</span>] { |
| <span class="kw">if </span>scaled(full_size.width, scale) >= requested_size.width || scaled(full_size.height, scale) >= requested_size.height { |
| <span class="kw">return </span>scale; |
| } |
| } |
| |
| <span class="number">8 |
| </span>} |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_choose_idct_size() { |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">200</span>, height: <span class="number">200</span>}), <span class="number">1</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">500</span>, height: <span class="number">500</span>}), <span class="number">1</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">684</span>, height: <span class="number">456</span>}), <span class="number">1</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">999</span>, height: <span class="number">456</span>}), <span class="number">1</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">684</span>, height: <span class="number">999</span>}), <span class="number">1</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">500</span>, height: <span class="number">333</span>}, Dimensions{width: <span class="number">63</span>, height: <span class="number">42</span>}), <span class="number">1</span>); |
| |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">685</span>, height: <span class="number">999</span>}), <span class="number">2</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">1000</span>, height: <span class="number">1000</span>}), <span class="number">2</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">1400</span>, height: <span class="number">1400</span>}), <span class="number">4</span>); |
| |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}), <span class="number">8</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">16384</span>, height: <span class="number">16384</span>}), <span class="number">8</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">1</span>, height: <span class="number">1</span>}, Dimensions{width: <span class="number">65535</span>, height: <span class="number">65535</span>}), <span class="number">8</span>); |
| <span class="macro">assert_eq!</span>(choose_idct_size(Dimensions{width: <span class="number">5472</span>, height: <span class="number">3648</span>}, Dimensions{width: <span class="number">16384</span>, height: <span class="number">16384</span>}), <span class="number">8</span>); |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>dequantize_and_idct_block(scale: usize, coefficients: <span class="kw-2">&</span>[i16], quantization_table: <span class="kw-2">&</span>[u16; <span class="number">64</span>], output_linestride: usize, output: <span class="kw-2">&mut </span>[u8]) { |
| <span class="kw">match </span>scale { |
| <span class="number">8 </span>=> dequantize_and_idct_block_8x8(coefficients, quantization_table, output_linestride, output), |
| <span class="number">4 </span>=> dequantize_and_idct_block_4x4(coefficients, quantization_table, output_linestride, output), |
| <span class="number">2 </span>=> dequantize_and_idct_block_2x2(coefficients, quantization_table, output_linestride, output), |
| <span class="number">1 </span>=> dequantize_and_idct_block_1x1(coefficients, quantization_table, output_linestride, output), |
| <span class="kw">_ </span>=> <span class="macro">panic!</span>(<span class="string">"Unsupported IDCT scale {}/8"</span>, scale), |
| } |
| } |
| |
| <span class="kw">pub fn </span>dequantize_and_idct_block_8x8( |
| coefficients: <span class="kw-2">&</span>[i16], |
| quantization_table: <span class="kw-2">&</span>[u16; <span class="number">64</span>], |
| output_linestride: usize, |
| output: <span class="kw-2">&mut </span>[u8] |
| ) { |
| <span class="kw">let </span>output = output |
| .chunks_mut(output_linestride); |
| dequantize_and_idct_block_8x8_inner(coefficients, quantization_table, output) |
| } |
| |
| <span class="comment">// This is based on stb_image's 'stbi__idct_block'. |
| </span><span class="kw">fn </span>dequantize_and_idct_block_8x8_inner<<span class="lifetime">'a</span>, I>( |
| coefficients: <span class="kw-2">&</span>[i16], |
| quantization_table: <span class="kw-2">&</span>[u16; <span class="number">64</span>], |
| output: I, |
| ) <span class="kw">where |
| </span>I: IntoIterator<Item = <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>[u8]>, |
| I::IntoIter: ExactSizeIterator<Item = <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>[u8]>, |
| { |
| <span class="kw">let </span>output = output.into_iter(); |
| <span class="macro">debug_assert!</span>( |
| output.len() >= <span class="number">8</span>, |
| <span class="string">"Output iterator has the wrong length: {}"</span>, |
| output.len() |
| ); |
| |
| <span class="comment">// optimizer hint to eliminate bounds checks within loops |
| </span><span class="macro">assert!</span>(coefficients.len() == <span class="number">64</span>); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>temp = [Wrapping(<span class="number">0</span>); <span class="number">64</span>]; |
| |
| <span class="comment">// columns |
| </span><span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..<span class="number">8 </span>{ |
| <span class="kw">if </span>coefficients[i + <span class="number">8</span>] == <span class="number">0 |
| </span>&& coefficients[i + <span class="number">16</span>] == <span class="number">0 |
| </span>&& coefficients[i + <span class="number">24</span>] == <span class="number">0 |
| </span>&& coefficients[i + <span class="number">32</span>] == <span class="number">0 |
| </span>&& coefficients[i + <span class="number">40</span>] == <span class="number">0 |
| </span>&& coefficients[i + <span class="number">48</span>] == <span class="number">0 |
| </span>&& coefficients[i + <span class="number">56</span>] == <span class="number">0 |
| </span>{ |
| <span class="kw">let </span>dcterm = dequantize(coefficients[i], quantization_table[i]) << <span class="number">2</span>; |
| temp[i] = dcterm; |
| temp[i + <span class="number">8</span>] = dcterm; |
| temp[i + <span class="number">16</span>] = dcterm; |
| temp[i + <span class="number">24</span>] = dcterm; |
| temp[i + <span class="number">32</span>] = dcterm; |
| temp[i + <span class="number">40</span>] = dcterm; |
| temp[i + <span class="number">48</span>] = dcterm; |
| temp[i + <span class="number">56</span>] = dcterm; |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span>s0 = dequantize(coefficients[i], quantization_table[i]); |
| <span class="kw">let </span>s1 = dequantize(coefficients[i + <span class="number">8</span>], quantization_table[i + <span class="number">8</span>]); |
| <span class="kw">let </span>s2 = dequantize(coefficients[i + <span class="number">16</span>], quantization_table[i + <span class="number">16</span>]); |
| <span class="kw">let </span>s3 = dequantize(coefficients[i + <span class="number">24</span>], quantization_table[i + <span class="number">24</span>]); |
| <span class="kw">let </span>s4 = dequantize(coefficients[i + <span class="number">32</span>], quantization_table[i + <span class="number">32</span>]); |
| <span class="kw">let </span>s5 = dequantize(coefficients[i + <span class="number">40</span>], quantization_table[i + <span class="number">40</span>]); |
| <span class="kw">let </span>s6 = dequantize(coefficients[i + <span class="number">48</span>], quantization_table[i + <span class="number">48</span>]); |
| <span class="kw">let </span>s7 = dequantize(coefficients[i + <span class="number">56</span>], quantization_table[i + <span class="number">56</span>]); |
| |
| <span class="kw">let </span>Kernel { |
| xs: [x0, x1, x2, x3], |
| ts: [t0, t1, t2, t3], |
| } = kernel( |
| [s0, s1, s2, s3, s4, s5, s6, s7], |
| <span class="comment">// constants scaled things up by 1<<12; let's bring them back |
| // down, but keep 2 extra bits of precision |
| </span><span class="number">512</span>, |
| ); |
| |
| temp[i] = (x0 + t3) >> <span class="number">10</span>; |
| temp[i + <span class="number">56</span>] = (x0 - t3) >> <span class="number">10</span>; |
| temp[i + <span class="number">8</span>] = (x1 + t2) >> <span class="number">10</span>; |
| temp[i + <span class="number">48</span>] = (x1 - t2) >> <span class="number">10</span>; |
| temp[i + <span class="number">16</span>] = (x2 + t1) >> <span class="number">10</span>; |
| temp[i + <span class="number">40</span>] = (x2 - t1) >> <span class="number">10</span>; |
| temp[i + <span class="number">24</span>] = (x3 + t0) >> <span class="number">10</span>; |
| temp[i + <span class="number">32</span>] = (x3 - t0) >> <span class="number">10</span>; |
| } |
| } |
| |
| <span class="kw">for </span>(chunk, output_chunk) <span class="kw">in </span>temp.chunks_exact(<span class="number">8</span>).zip(output) { |
| <span class="kw">let </span>chunk = <<span class="kw-2">&</span>[<span class="kw">_</span>; <span class="number">8</span>]>::try_from(chunk).unwrap(); |
| |
| <span class="comment">// constants scaled things up by 1<<12, plus we had 1<<2 from first |
| // loop, plus horizontal and vertical each scale by sqrt(8) so together |
| // we've got an extra 1<<3, so 1<<17 total we need to remove. |
| // so we want to round that, which means adding 0.5 * 1<<17, |
| // aka 65536. Also, we'll end up with -128 to 127 that we want |
| // to encode as 0..255 by adding 128, so we'll add that before the shift |
| </span><span class="kw">const </span>X_SCALE: i32 = <span class="number">65536 </span>+ (<span class="number">128 </span><< <span class="number">17</span>); |
| |
| <span class="comment">// TODO When the minimum rust version supports it |
| // let [s0, rest @ ..] = chunk; |
| </span><span class="kw">let </span>(s0, rest) = chunk.split_first().unwrap(); |
| <span class="kw">if </span><span class="kw-2">*</span>rest == [Wrapping(<span class="number">0</span>); <span class="number">7</span>] { |
| <span class="kw">let </span>dcterm = stbi_clamp((stbi_fsh(<span class="kw-2">*</span>s0) + Wrapping(X_SCALE)) >> <span class="number">17</span>); |
| output_chunk[<span class="number">0</span>] = dcterm; |
| output_chunk[<span class="number">1</span>] = dcterm; |
| output_chunk[<span class="number">2</span>] = dcterm; |
| output_chunk[<span class="number">3</span>] = dcterm; |
| output_chunk[<span class="number">4</span>] = dcterm; |
| output_chunk[<span class="number">5</span>] = dcterm; |
| output_chunk[<span class="number">6</span>] = dcterm; |
| output_chunk[<span class="number">7</span>] = dcterm; |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span>Kernel { |
| xs: [x0, x1, x2, x3], |
| ts: [t0, t1, t2, t3], |
| } = kernel(<span class="kw-2">*</span>chunk, X_SCALE); |
| |
| output_chunk[<span class="number">0</span>] = stbi_clamp((x0 + t3) >> <span class="number">17</span>); |
| output_chunk[<span class="number">7</span>] = stbi_clamp((x0 - t3) >> <span class="number">17</span>); |
| output_chunk[<span class="number">1</span>] = stbi_clamp((x1 + t2) >> <span class="number">17</span>); |
| output_chunk[<span class="number">6</span>] = stbi_clamp((x1 - t2) >> <span class="number">17</span>); |
| output_chunk[<span class="number">2</span>] = stbi_clamp((x2 + t1) >> <span class="number">17</span>); |
| output_chunk[<span class="number">5</span>] = stbi_clamp((x2 - t1) >> <span class="number">17</span>); |
| output_chunk[<span class="number">3</span>] = stbi_clamp((x3 + t0) >> <span class="number">17</span>); |
| output_chunk[<span class="number">4</span>] = stbi_clamp((x3 - t0) >> <span class="number">17</span>); |
| } |
| } |
| } |
| |
| <span class="kw">struct </span>Kernel { |
| xs: [Wrapping<i32>; <span class="number">4</span>], |
| ts: [Wrapping<i32>; <span class="number">4</span>], |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>kernel_x([s0, s2, s4, s6]: [Wrapping<i32>; <span class="number">4</span>], x_scale: i32) -> [Wrapping<i32>; <span class="number">4</span>] { |
| <span class="comment">// Even `chunk` indicies |
| </span><span class="kw">let </span>(t2, t3); |
| { |
| <span class="kw">let </span>p2 = s2; |
| <span class="kw">let </span>p3 = s6; |
| |
| <span class="kw">let </span>p1 = (p2 + p3) * stbi_f2f(<span class="number">0.5411961</span>); |
| t2 = p1 + p3 * stbi_f2f(-<span class="number">1.847759065</span>); |
| t3 = p1 + p2 * stbi_f2f(<span class="number">0.765366865</span>); |
| } |
| |
| <span class="kw">let </span>(t0, t1); |
| { |
| <span class="kw">let </span>p2 = s0; |
| <span class="kw">let </span>p3 = s4; |
| |
| t0 = stbi_fsh(p2 + p3); |
| t1 = stbi_fsh(p2 - p3); |
| } |
| |
| <span class="kw">let </span>x0 = t0 + t3; |
| <span class="kw">let </span>x3 = t0 - t3; |
| <span class="kw">let </span>x1 = t1 + t2; |
| <span class="kw">let </span>x2 = t1 - t2; |
| |
| <span class="kw">let </span>x_scale = Wrapping(x_scale); |
| |
| [x0 + x_scale, x1 + x_scale, x2 + x_scale, x3 + x_scale] |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>kernel_t([s1, s3, s5, s7]: [Wrapping<i32>; <span class="number">4</span>]) -> [Wrapping<i32>; <span class="number">4</span>] { |
| <span class="comment">// Odd `chunk` indicies |
| </span><span class="kw">let </span><span class="kw-2">mut </span>t0 = s7; |
| <span class="kw">let </span><span class="kw-2">mut </span>t1 = s5; |
| <span class="kw">let </span><span class="kw-2">mut </span>t2 = s3; |
| <span class="kw">let </span><span class="kw-2">mut </span>t3 = s1; |
| |
| <span class="kw">let </span>p3 = t0 + t2; |
| <span class="kw">let </span>p4 = t1 + t3; |
| <span class="kw">let </span>p1 = t0 + t3; |
| <span class="kw">let </span>p2 = t1 + t2; |
| <span class="kw">let </span>p5 = (p3 + p4) * stbi_f2f(<span class="number">1.175875602</span>); |
| |
| t0 <span class="kw-2">*</span>= stbi_f2f(<span class="number">0.298631336</span>); |
| t1 <span class="kw-2">*</span>= stbi_f2f(<span class="number">2.053119869</span>); |
| t2 <span class="kw-2">*</span>= stbi_f2f(<span class="number">3.072711026</span>); |
| t3 <span class="kw-2">*</span>= stbi_f2f(<span class="number">1.501321110</span>); |
| |
| <span class="kw">let </span>p1 = p5 + p1 * stbi_f2f(-<span class="number">0.899976223</span>); |
| <span class="kw">let </span>p2 = p5 + p2 * stbi_f2f(-<span class="number">2.562915447</span>); |
| <span class="kw">let </span>p3 = p3 * stbi_f2f(-<span class="number">1.961570560</span>); |
| <span class="kw">let </span>p4 = p4 * stbi_f2f(-<span class="number">0.390180644</span>); |
| |
| t3 += p1 + p4; |
| t2 += p2 + p3; |
| t1 += p2 + p4; |
| t0 += p1 + p3; |
| |
| [t0, t1, t2, t3] |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>kernel([s0, s1, s2, s3, s4, s5, s6, s7]: [Wrapping<i32>; <span class="number">8</span>], x_scale: i32) -> Kernel { |
| Kernel { |
| xs: kernel_x([s0, s2, s4, s6], x_scale), |
| ts: kernel_t([s1, s3, s5, s7]), |
| } |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>dequantize(c: i16, q: u16) -> Wrapping<i32> { |
| Wrapping(i32::from(c) * i32::from(q)) |
| } |
| |
| <span class="comment">// 4x4 and 2x2 IDCT based on Rakesh Dugad and Narendra Ahuja: "A Fast Scheme for Image Size Change in the Compressed Domain" (2001). |
| // http://sylvana.net/jpegcrop/jidctred/ |
| </span><span class="kw">fn </span>dequantize_and_idct_block_4x4(coefficients: <span class="kw-2">&</span>[i16], quantization_table: <span class="kw-2">&</span>[u16; <span class="number">64</span>], output_linestride: usize, output: <span class="kw-2">&mut </span>[u8]) { |
| <span class="macro">debug_assert_eq!</span>(coefficients.len(), <span class="number">64</span>); |
| <span class="kw">let </span><span class="kw-2">mut </span>temp = [Wrapping(<span class="number">0i32</span>); <span class="number">4 </span>* <span class="number">4</span>]; |
| |
| <span class="kw">const </span>CONST_BITS: usize = <span class="number">12</span>; |
| <span class="kw">const </span>PASS1_BITS: usize = <span class="number">2</span>; |
| <span class="kw">const </span>FINAL_BITS: usize = CONST_BITS + PASS1_BITS + <span class="number">3</span>; |
| |
| <span class="comment">// columns |
| </span><span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..<span class="number">4 </span>{ |
| <span class="kw">let </span>s0 = Wrapping(coefficients[i + <span class="number">8 </span>* <span class="number">0</span>] <span class="kw">as </span>i32 * quantization_table[i + <span class="number">8 </span>* <span class="number">0</span>] <span class="kw">as </span>i32); |
| <span class="kw">let </span>s1 = Wrapping(coefficients[i + <span class="number">8 </span>* <span class="number">1</span>] <span class="kw">as </span>i32 * quantization_table[i + <span class="number">8 </span>* <span class="number">1</span>] <span class="kw">as </span>i32); |
| <span class="kw">let </span>s2 = Wrapping(coefficients[i + <span class="number">8 </span>* <span class="number">2</span>] <span class="kw">as </span>i32 * quantization_table[i + <span class="number">8 </span>* <span class="number">2</span>] <span class="kw">as </span>i32); |
| <span class="kw">let </span>s3 = Wrapping(coefficients[i + <span class="number">8 </span>* <span class="number">3</span>] <span class="kw">as </span>i32 * quantization_table[i + <span class="number">8 </span>* <span class="number">3</span>] <span class="kw">as </span>i32); |
| |
| <span class="kw">let </span>x0 = (s0 + s2) << PASS1_BITS; |
| <span class="kw">let </span>x2 = (s0 - s2) << PASS1_BITS; |
| |
| <span class="kw">let </span>p1 = (s1 + s3) * stbi_f2f(<span class="number">0.541196100</span>); |
| <span class="kw">let </span>t0 = (p1 + s3 * stbi_f2f(-<span class="number">1.847759065</span>) + Wrapping(<span class="number">512</span>)) >> (CONST_BITS - PASS1_BITS); |
| <span class="kw">let </span>t2 = (p1 + s1 * stbi_f2f(<span class="number">0.765366865</span>) + Wrapping(<span class="number">512</span>)) >> (CONST_BITS - PASS1_BITS); |
| |
| temp[i + <span class="number">4 </span>* <span class="number">0</span>] = x0 + t2; |
| temp[i + <span class="number">4 </span>* <span class="number">3</span>] = x0 - t2; |
| temp[i + <span class="number">4 </span>* <span class="number">1</span>] = x2 + t0; |
| temp[i + <span class="number">4 </span>* <span class="number">2</span>] = x2 - t0; |
| } |
| |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0 </span>.. <span class="number">4 </span>{ |
| <span class="kw">let </span>s0 = temp[i * <span class="number">4 </span>+ <span class="number">0</span>]; |
| <span class="kw">let </span>s1 = temp[i * <span class="number">4 </span>+ <span class="number">1</span>]; |
| <span class="kw">let </span>s2 = temp[i * <span class="number">4 </span>+ <span class="number">2</span>]; |
| <span class="kw">let </span>s3 = temp[i * <span class="number">4 </span>+ <span class="number">3</span>]; |
| |
| <span class="kw">let </span>x0 = (s0 + s2) << CONST_BITS; |
| <span class="kw">let </span>x2 = (s0 - s2) << CONST_BITS; |
| |
| <span class="kw">let </span>p1 = (s1 + s3) * stbi_f2f(<span class="number">0.541196100</span>); |
| <span class="kw">let </span>t0 = p1 + s3 * stbi_f2f(-<span class="number">1.847759065</span>); |
| <span class="kw">let </span>t2 = p1 + s1 * stbi_f2f(<span class="number">0.765366865</span>); |
| |
| <span class="comment">// constants scaled things up by 1<<12, plus we had 1<<2 from first |
| // loop, plus horizontal and vertical each scale by sqrt(8) so together |
| // we've got an extra 1<<3, so 1<<17 total we need to remove. |
| // so we want to round that, which means adding 0.5 * 1<<17, |
| // aka 65536. Also, we'll end up with -128 to 127 that we want |
| // to encode as 0..255 by adding 128, so we'll add that before the shift |
| </span><span class="kw">let </span>x0 = x0 + Wrapping(<span class="number">1 </span><< (FINAL_BITS - <span class="number">1</span>)) + Wrapping(<span class="number">128 </span><< FINAL_BITS); |
| <span class="kw">let </span>x2 = x2 + Wrapping(<span class="number">1 </span><< (FINAL_BITS - <span class="number">1</span>)) + Wrapping(<span class="number">128 </span><< FINAL_BITS); |
| |
| output[i * output_linestride + <span class="number">0</span>] = stbi_clamp((x0 + t2) >> FINAL_BITS); |
| output[i * output_linestride + <span class="number">3</span>] = stbi_clamp((x0 - t2) >> FINAL_BITS); |
| output[i * output_linestride + <span class="number">1</span>] = stbi_clamp((x2 + t0) >> FINAL_BITS); |
| output[i * output_linestride + <span class="number">2</span>] = stbi_clamp((x2 - t0) >> FINAL_BITS); |
| } |
| } |
| |
| <span class="kw">fn </span>dequantize_and_idct_block_2x2(coefficients: <span class="kw-2">&</span>[i16], quantization_table: <span class="kw-2">&</span>[u16; <span class="number">64</span>], output_linestride: usize, output: <span class="kw-2">&mut </span>[u8]) { |
| <span class="macro">debug_assert_eq!</span>(coefficients.len(), <span class="number">64</span>); |
| |
| <span class="kw">const </span>SCALE_BITS: usize = <span class="number">3</span>; |
| |
| <span class="comment">// Column 0 |
| </span><span class="kw">let </span>s00 = Wrapping(coefficients[<span class="number">8 </span>* <span class="number">0</span>] <span class="kw">as </span>i32 * quantization_table[<span class="number">8 </span>* <span class="number">0</span>] <span class="kw">as </span>i32); |
| <span class="kw">let </span>s10 = Wrapping(coefficients[<span class="number">8 </span>* <span class="number">1</span>] <span class="kw">as </span>i32 * quantization_table[<span class="number">8 </span>* <span class="number">1</span>] <span class="kw">as </span>i32); |
| |
| <span class="kw">let </span>x0 = s00 + s10; |
| <span class="kw">let </span>x2 = s00 - s10; |
| |
| <span class="comment">// Column 1 |
| </span><span class="kw">let </span>s01 = Wrapping(coefficients[<span class="number">8 </span>* <span class="number">0 </span>+ <span class="number">1</span>] <span class="kw">as </span>i32 * quantization_table[<span class="number">8 </span>* <span class="number">0 </span>+ <span class="number">1</span>] <span class="kw">as </span>i32); |
| <span class="kw">let </span>s11 = Wrapping(coefficients[<span class="number">8 </span>* <span class="number">1 </span>+ <span class="number">1</span>] <span class="kw">as </span>i32 * quantization_table[<span class="number">8 </span>* <span class="number">1 </span>+ <span class="number">1</span>] <span class="kw">as </span>i32); |
| |
| <span class="kw">let </span>x1 = s01 + s11; |
| <span class="kw">let </span>x3 = s01 - s11; |
| |
| <span class="kw">let </span>x0 = x0 + Wrapping(<span class="number">1 </span><< (SCALE_BITS - <span class="number">1</span>)) + Wrapping(<span class="number">128 </span><< SCALE_BITS); |
| <span class="kw">let </span>x2 = x2 + Wrapping(<span class="number">1 </span><< (SCALE_BITS - <span class="number">1</span>)) + Wrapping(<span class="number">128 </span><< SCALE_BITS); |
| |
| <span class="comment">// Row 0 |
| </span>output[<span class="number">0</span>] = stbi_clamp((x0 + x1) >> SCALE_BITS); |
| output[<span class="number">1</span>] = stbi_clamp((x0 - x1) >> SCALE_BITS); |
| |
| <span class="comment">// Row 1 |
| </span>output[output_linestride + <span class="number">0</span>] = stbi_clamp((x2 + x3) >> SCALE_BITS); |
| output[output_linestride + <span class="number">1</span>] = stbi_clamp((x2 - x3) >> SCALE_BITS); |
| } |
| |
| <span class="kw">fn </span>dequantize_and_idct_block_1x1(coefficients: <span class="kw-2">&</span>[i16], quantization_table: <span class="kw-2">&</span>[u16; <span class="number">64</span>], _output_linestride: usize, output: <span class="kw-2">&mut </span>[u8]) { |
| <span class="macro">debug_assert_eq!</span>(coefficients.len(), <span class="number">64</span>); |
| |
| <span class="kw">let </span>s0 = (Wrapping(coefficients[<span class="number">0</span>] <span class="kw">as </span>i32 * quantization_table[<span class="number">0</span>] <span class="kw">as </span>i32) + Wrapping(<span class="number">128 </span>* <span class="number">8</span>)) / Wrapping(<span class="number">8</span>); |
| output[<span class="number">0</span>] = stbi_clamp(s0); |
| } |
| |
| <span class="comment">// take a -128..127 value and stbi__clamp it and convert to 0..255 |
| </span><span class="kw">fn </span>stbi_clamp(x: Wrapping<i32>) -> u8 |
| { |
| x.<span class="number">0</span>.max(<span class="number">0</span>).min(<span class="number">255</span>) <span class="kw">as </span>u8 |
| } |
| |
| <span class="kw">fn </span>stbi_f2f(x: f32) -> Wrapping<i32> { |
| Wrapping((x * <span class="number">4096.0 </span>+ <span class="number">0.5</span>) <span class="kw">as </span>i32) |
| } |
| |
| <span class="kw">fn </span>stbi_fsh(x: Wrapping<i32>) -> Wrapping<i32> { |
| x << <span class="number">12 |
| </span>} |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_dequantize_and_idct_block_8x8() { |
| <span class="kw">let </span>coefficients: [i16; <span class="number">8 </span>* <span class="number">8</span>] = [ |
| -<span class="number">14</span>, -<span class="number">39</span>, <span class="number">58</span>, -<span class="number">2</span>, <span class="number">3</span>, <span class="number">3</span>, <span class="number">0</span>, <span class="number">1</span>, |
| <span class="number">11</span>, <span class="number">27</span>, <span class="number">4</span>, -<span class="number">3</span>, <span class="number">3</span>, <span class="number">0</span>, <span class="number">1</span>, <span class="number">0</span>, |
| -<span class="number">6</span>, -<span class="number">13</span>, -<span class="number">9</span>, -<span class="number">1</span>, -<span class="number">2</span>, -<span class="number">1</span>, <span class="number">0</span>, <span class="number">0</span>, |
| -<span class="number">4</span>, <span class="number">0</span>, -<span class="number">1</span>, -<span class="number">2</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, |
| <span class="number">3</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, |
| -<span class="number">3</span>, -<span class="number">2</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>]; |
| |
| <span class="kw">let </span>quantization_table: [u16; <span class="number">8 </span>* <span class="number">8</span>] = [ |
| <span class="number">8</span>, <span class="number">6</span>, <span class="number">5</span>, <span class="number">8</span>, <span class="number">12</span>, <span class="number">20</span>, <span class="number">26</span>, <span class="number">31</span>, |
| <span class="number">6</span>, <span class="number">6</span>, <span class="number">7</span>, <span class="number">10</span>, <span class="number">13</span>, <span class="number">29</span>, <span class="number">30</span>, <span class="number">28</span>, |
| <span class="number">7</span>, <span class="number">7</span>, <span class="number">8</span>, <span class="number">12</span>, <span class="number">20</span>, <span class="number">29</span>, <span class="number">35</span>, <span class="number">28</span>, |
| <span class="number">7</span>, <span class="number">9</span>, <span class="number">11</span>, <span class="number">15</span>, <span class="number">26</span>, <span class="number">44</span>, <span class="number">40</span>, <span class="number">31</span>, |
| <span class="number">9</span>, <span class="number">11</span>, <span class="number">19</span>, <span class="number">28</span>, <span class="number">34</span>, <span class="number">55</span>, <span class="number">52</span>, <span class="number">39</span>, |
| <span class="number">12</span>, <span class="number">18</span>, <span class="number">28</span>, <span class="number">32</span>, <span class="number">41</span>, <span class="number">52</span>, <span class="number">57</span>, <span class="number">46</span>, |
| <span class="number">25</span>, <span class="number">32</span>, <span class="number">39</span>, <span class="number">44</span>, <span class="number">52</span>, <span class="number">61</span>, <span class="number">60</span>, <span class="number">51</span>, |
| <span class="number">36</span>, <span class="number">46</span>, <span class="number">48</span>, <span class="number">49</span>, <span class="number">56</span>, <span class="number">50</span>, <span class="number">52</span>, <span class="number">50</span>]; |
| <span class="kw">let </span>output_linestride: usize = <span class="number">8</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>output = [<span class="number">0u8</span>; <span class="number">8 </span>* <span class="number">8</span>]; |
| dequantize_and_idct_block_8x8( |
| <span class="kw-2">&</span>coefficients, |
| <span class="kw-2">&</span>quantization_table, |
| output_linestride, |
| <span class="kw-2">&mut </span>output); |
| <span class="kw">let </span>expected_output = [ |
| <span class="number">118</span>, <span class="number">92</span>, <span class="number">110</span>, <span class="number">83</span>, <span class="number">77</span>, <span class="number">93</span>, <span class="number">144</span>, <span class="number">198</span>, |
| <span class="number">172</span>, <span class="number">116</span>, <span class="number">114</span>, <span class="number">87</span>, <span class="number">78</span>, <span class="number">93</span>, <span class="number">146</span>, <span class="number">191</span>, |
| <span class="number">194</span>, <span class="number">107</span>, <span class="number">91</span>, <span class="number">76</span>, <span class="number">71</span>, <span class="number">93</span>, <span class="number">160</span>, <span class="number">198</span>, |
| <span class="number">196</span>, <span class="number">100</span>, <span class="number">80</span>, <span class="number">74</span>, <span class="number">67</span>, <span class="number">92</span>, <span class="number">174</span>, <span class="number">209</span>, |
| <span class="number">182</span>, <span class="number">104</span>, <span class="number">88</span>, <span class="number">81</span>, <span class="number">68</span>, <span class="number">89</span>, <span class="number">178</span>, <span class="number">206</span>, |
| <span class="number">105</span>, <span class="number">64</span>, <span class="number">59</span>, <span class="number">59</span>, <span class="number">63</span>, <span class="number">94</span>, <span class="number">183</span>, <span class="number">201</span>, |
| <span class="number">35</span>, <span class="number">27</span>, <span class="number">28</span>, <span class="number">37</span>, <span class="number">72</span>, <span class="number">121</span>, <span class="number">203</span>, <span class="number">204</span>, |
| <span class="number">37</span>, <span class="number">45</span>, <span class="number">41</span>, <span class="number">47</span>, <span class="number">98</span>, <span class="number">154</span>, <span class="number">223</span>, <span class="number">208</span>]; |
| <span class="macro">assert_eq!</span>(<span class="kw-2">&</span>output[..], <span class="kw-2">&</span>expected_output[..]); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_dequantize_and_idct_block_8x8_all_zero() { |
| <span class="kw">let </span><span class="kw-2">mut </span>output = [<span class="number">0u8</span>; <span class="number">8 </span>* <span class="number">8</span>]; |
| dequantize_and_idct_block_8x8( |
| <span class="kw-2">&</span>[<span class="number">0</span>; <span class="number">8</span><span class="kw-2">*</span><span class="number">8</span>], |
| <span class="kw-2">&</span>[<span class="number">666</span>; <span class="number">8</span><span class="kw-2">*</span><span class="number">8</span>], |
| <span class="number">8</span>, |
| <span class="kw-2">&mut </span>output); |
| <span class="macro">assert_eq!</span>(<span class="kw-2">&</span>output[..], <span class="kw-2">&</span>[<span class="number">128</span>; <span class="number">8</span><span class="kw-2">*</span><span class="number">8</span>][..]); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_dequantize_and_idct_block_8x8_saturated() { |
| <span class="kw">let </span><span class="kw-2">mut </span>output = [<span class="number">0u8</span>; <span class="number">8 </span>* <span class="number">8</span>]; |
| dequantize_and_idct_block_8x8( |
| <span class="kw-2">&</span>[std::i16::MAX; <span class="number">8</span><span class="kw-2">*</span><span class="number">8</span>], |
| <span class="kw-2">&</span>[std::u16::MAX; <span class="number">8</span><span class="kw-2">*</span><span class="number">8</span>], |
| <span class="number">8</span>, |
| <span class="kw-2">&mut </span>output); |
| <span class="kw">let </span>expected = [ |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">215</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">0</span>, |
| <span class="number">255</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">255</span>, |
| <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">0</span>, |
| <span class="number">255</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">255</span>, <span class="number">170</span>, <span class="number">0</span>, |
| <span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">255</span>, |
| <span class="number">255</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">255</span>, <span class="number">0</span>, <span class="number">0</span>]; |
| <span class="macro">assert_eq!</span>(<span class="kw-2">&</span>output[..], <span class="kw-2">&</span>expected[..]); |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="jpeg_decoder" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
