| <!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/image-0.23.14/./src/codecs/jpeg/transform.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>transform.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="../../../../image/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="../../../../image/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">/* |
| fdct is a Rust translation of jfdctint.c from the |
| Independent JPEG Group's libjpeg version 9a |
| obtained from http://www.ijg.org/files/jpegsr9a.zip |
| It comes with the following conditions of distribution and use: |
| |
| In plain English: |
| |
| 1. We don't promise that this software works. (But if you find any bugs, |
| please let us know!) |
| 2. You can use this software for whatever you want. You don't have to pay us. |
| 3. You may not pretend that you wrote this software. If you use it in a |
| program, you must acknowledge somewhere in your documentation that |
| you've used the IJG code. |
| |
| In legalese: |
| |
| The authors make NO WARRANTY or representation, either express or implied, |
| with respect to this software, its quality, accuracy, merchantability, or |
| fitness for a particular purpose. This software is provided "AS IS", and you, |
| its user, assume the entire risk as to its quality and accuracy. |
| |
| This software is copyright (C) 1991-2014, Thomas G. Lane, Guido Vollbeding. |
| All Rights Reserved except as specified below. |
| |
| Permission is hereby granted to use, copy, modify, and distribute this |
| software (or portions thereof) for any purpose, without fee, subject to these |
| conditions: |
| (1) If any part of the source code for this software is distributed, then this |
| README file must be included, with this copyright and no-warranty notice |
| unaltered; and any additions, deletions, or changes to the original files |
| must be clearly indicated in accompanying documentation. |
| (2) If only executable code is distributed, then the accompanying |
| documentation must state that "this software is based in part on the work of |
| the Independent JPEG Group". |
| (3) Permission for use of this software is granted only if the user accepts |
| full responsibility for any undesirable consequences; the authors accept |
| NO LIABILITY for damages of any kind. |
| |
| These conditions apply to any software derived from or based on the IJG code, |
| not just to the unmodified library. If you use our work, you ought to |
| acknowledge us. |
| |
| Permission is NOT granted for the use of any IJG author's name or company name |
| in advertising or publicity relating to this software or products derived from |
| it. This software may be referred to only as "the Independent JPEG Group's |
| software". |
| |
| We specifically permit and encourage the use of this software as the basis of |
| commercial products, provided that all warranty or liability claims are |
| assumed by the product vendor. |
| */ |
| |
| </span><span class="kw">static </span>CONST_BITS: i32 = <span class="number">13</span>; |
| <span class="kw">static </span>PASS1_BITS: i32 = <span class="number">2</span>; |
| |
| <span class="kw">static </span>FIX_0_298631336: i32 = <span class="number">2446</span>; |
| <span class="kw">static </span>FIX_0_390180644: i32 = <span class="number">3196</span>; |
| <span class="kw">static </span>FIX_0_541196100: i32 = <span class="number">4433</span>; |
| <span class="kw">static </span>FIX_0_765366865: i32 = <span class="number">6270</span>; |
| <span class="kw">static </span>FIX_0_899976223: i32 = <span class="number">7373</span>; |
| <span class="kw">static </span>FIX_1_175875602: i32 = <span class="number">9633</span>; |
| <span class="kw">static </span>FIX_1_501321110: i32 = <span class="number">12_299</span>; |
| <span class="kw">static </span>FIX_1_847759065: i32 = <span class="number">15_137</span>; |
| <span class="kw">static </span>FIX_1_961570560: i32 = <span class="number">16_069</span>; |
| <span class="kw">static </span>FIX_2_053119869: i32 = <span class="number">16_819</span>; |
| <span class="kw">static </span>FIX_2_562915447: i32 = <span class="number">20_995</span>; |
| <span class="kw">static </span>FIX_3_072711026: i32 = <span class="number">25_172</span>; |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>fdct(samples: <span class="kw-2">&</span>[u8; <span class="number">64</span>], coeffs: <span class="kw-2">&mut </span>[i32; <span class="number">64</span>]) { |
| <span class="comment">// Pass 1: process rows. |
| // Results are scaled by sqrt(8) compared to a true DCT |
| // furthermore we scale the results by 2**PASS1_BITS |
| </span><span class="kw">for </span>y <span class="kw">in </span><span class="number">0usize</span>..<span class="number">8 </span>{ |
| <span class="kw">let </span>y0 = y * <span class="number">8</span>; |
| |
| <span class="comment">// Even part |
| </span><span class="kw">let </span>t0 = i32::from(samples[y0]) + i32::from(samples[y0 + <span class="number">7</span>]); |
| <span class="kw">let </span>t1 = i32::from(samples[y0 + <span class="number">1</span>]) + i32::from(samples[y0 + <span class="number">6</span>]); |
| <span class="kw">let </span>t2 = i32::from(samples[y0 + <span class="number">2</span>]) + i32::from(samples[y0 + <span class="number">5</span>]); |
| <span class="kw">let </span>t3 = i32::from(samples[y0 + <span class="number">3</span>]) + i32::from(samples[y0 + <span class="number">4</span>]); |
| |
| <span class="kw">let </span>t10 = t0 + t3; |
| <span class="kw">let </span>t12 = t0 - t3; |
| <span class="kw">let </span>t11 = t1 + t2; |
| <span class="kw">let </span>t13 = t1 - t2; |
| |
| <span class="kw">let </span>t0 = i32::from(samples[y0]) - i32::from(samples[y0 + <span class="number">7</span>]); |
| <span class="kw">let </span>t1 = i32::from(samples[y0 + <span class="number">1</span>]) - i32::from(samples[y0 + <span class="number">6</span>]); |
| <span class="kw">let </span>t2 = i32::from(samples[y0 + <span class="number">2</span>]) - i32::from(samples[y0 + <span class="number">5</span>]); |
| <span class="kw">let </span>t3 = i32::from(samples[y0 + <span class="number">3</span>]) - i32::from(samples[y0 + <span class="number">4</span>]); |
| |
| <span class="comment">// Apply unsigned -> signed conversion |
| </span>coeffs[y0] = (t10 + t11 - <span class="number">8 </span>* <span class="number">128</span>) << PASS1_BITS <span class="kw">as </span>usize; |
| coeffs[y0 + <span class="number">4</span>] = (t10 - t11) << PASS1_BITS <span class="kw">as </span>usize; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>z1 = (t12 + t13) * FIX_0_541196100; |
| <span class="comment">// Add fudge factor here for final descale |
| </span>z1 += <span class="number">1 </span><< (CONST_BITS - PASS1_BITS - <span class="number">1</span>) <span class="kw">as </span>usize; |
| |
| coeffs[y0 + <span class="number">2</span>] = (z1 + t12 * FIX_0_765366865) >> (CONST_BITS - PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[y0 + <span class="number">6</span>] = (z1 - t13 * FIX_1_847759065) >> (CONST_BITS - PASS1_BITS) <span class="kw">as </span>usize; |
| |
| <span class="comment">// Odd part |
| </span><span class="kw">let </span>t12 = t0 + t2; |
| <span class="kw">let </span>t13 = t1 + t3; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>z1 = (t12 + t13) * FIX_1_175875602; |
| <span class="comment">// Add fudge factor here for final descale |
| </span>z1 += <span class="number">1 </span><< (CONST_BITS - PASS1_BITS - <span class="number">1</span>) <span class="kw">as </span>usize; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>t12 = t12 * (-FIX_0_390180644); |
| <span class="kw">let </span><span class="kw-2">mut </span>t13 = t13 * (-FIX_1_961570560); |
| t12 += z1; |
| t13 += z1; |
| |
| <span class="kw">let </span>z1 = (t0 + t3) * (-FIX_0_899976223); |
| <span class="kw">let </span><span class="kw-2">mut </span>t0 = t0 * FIX_1_501321110; |
| <span class="kw">let </span><span class="kw-2">mut </span>t3 = t3 * FIX_0_298631336; |
| t0 += z1 + t12; |
| t3 += z1 + t13; |
| |
| <span class="kw">let </span>z1 = (t1 + t2) * (-FIX_2_562915447); |
| <span class="kw">let </span><span class="kw-2">mut </span>t1 = t1 * FIX_3_072711026; |
| <span class="kw">let </span><span class="kw-2">mut </span>t2 = t2 * FIX_2_053119869; |
| t1 += z1 + t13; |
| t2 += z1 + t12; |
| |
| coeffs[y0 + <span class="number">1</span>] = t0 >> (CONST_BITS - PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[y0 + <span class="number">3</span>] = t1 >> (CONST_BITS - PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[y0 + <span class="number">5</span>] = t2 >> (CONST_BITS - PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[y0 + <span class="number">7</span>] = t3 >> (CONST_BITS - PASS1_BITS) <span class="kw">as </span>usize; |
| } |
| |
| <span class="comment">// Pass 2: process columns |
| // We remove the PASS1_BITS scaling but leave the results scaled up an |
| // overall factor of 8 |
| </span><span class="kw">for </span>x <span class="kw">in </span>(<span class="number">0usize</span>..<span class="number">8</span>).rev() { |
| <span class="comment">// Even part |
| </span><span class="kw">let </span>t0 = coeffs[x] + coeffs[x + <span class="number">8 </span>* <span class="number">7</span>]; |
| <span class="kw">let </span>t1 = coeffs[x + <span class="number">8</span>] + coeffs[x + <span class="number">8 </span>* <span class="number">6</span>]; |
| <span class="kw">let </span>t2 = coeffs[x + <span class="number">8 </span>* <span class="number">2</span>] + coeffs[x + <span class="number">8 </span>* <span class="number">5</span>]; |
| <span class="kw">let </span>t3 = coeffs[x + <span class="number">8 </span>* <span class="number">3</span>] + coeffs[x + <span class="number">8 </span>* <span class="number">4</span>]; |
| |
| <span class="comment">// Add fudge factor here for final descale |
| </span><span class="kw">let </span>t10 = t0 + t3 + (<span class="number">1 </span><< (PASS1_BITS - <span class="number">1</span>) <span class="kw">as </span>usize); |
| <span class="kw">let </span>t12 = t0 - t3; |
| <span class="kw">let </span>t11 = t1 + t2; |
| <span class="kw">let </span>t13 = t1 - t2; |
| |
| <span class="kw">let </span>t0 = coeffs[x] - coeffs[x + <span class="number">8 </span>* <span class="number">7</span>]; |
| <span class="kw">let </span>t1 = coeffs[x + <span class="number">8</span>] - coeffs[x + <span class="number">8 </span>* <span class="number">6</span>]; |
| <span class="kw">let </span>t2 = coeffs[x + <span class="number">8 </span>* <span class="number">2</span>] - coeffs[x + <span class="number">8 </span>* <span class="number">5</span>]; |
| <span class="kw">let </span>t3 = coeffs[x + <span class="number">8 </span>* <span class="number">3</span>] - coeffs[x + <span class="number">8 </span>* <span class="number">4</span>]; |
| |
| coeffs[x] = (t10 + t11) >> PASS1_BITS <span class="kw">as </span>usize; |
| coeffs[x + <span class="number">8 </span>* <span class="number">4</span>] = (t10 - t11) >> PASS1_BITS <span class="kw">as </span>usize; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>z1 = (t12 + t13) * FIX_0_541196100; |
| <span class="comment">// Add fudge factor here for final descale |
| </span>z1 += <span class="number">1 </span><< (CONST_BITS + PASS1_BITS - <span class="number">1</span>) <span class="kw">as </span>usize; |
| |
| coeffs[x + <span class="number">8 </span>* <span class="number">2</span>] = (z1 + t12 * FIX_0_765366865) >> (CONST_BITS + PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[x + <span class="number">8 </span>* <span class="number">6</span>] = (z1 - t13 * FIX_1_847759065) >> (CONST_BITS + PASS1_BITS) <span class="kw">as </span>usize; |
| |
| <span class="comment">// Odd part |
| </span><span class="kw">let </span>t12 = t0 + t2; |
| <span class="kw">let </span>t13 = t1 + t3; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>z1 = (t12 + t13) * FIX_1_175875602; |
| <span class="comment">// Add fudge factor here for final descale |
| </span>z1 += <span class="number">1 </span><< (CONST_BITS - PASS1_BITS - <span class="number">1</span>) <span class="kw">as </span>usize; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>t12 = t12 * (-FIX_0_390180644); |
| <span class="kw">let </span><span class="kw-2">mut </span>t13 = t13 * (-FIX_1_961570560); |
| t12 += z1; |
| t13 += z1; |
| |
| <span class="kw">let </span>z1 = (t0 + t3) * (-FIX_0_899976223); |
| <span class="kw">let </span><span class="kw-2">mut </span>t0 = t0 * FIX_1_501321110; |
| <span class="kw">let </span><span class="kw-2">mut </span>t3 = t3 * FIX_0_298631336; |
| t0 += z1 + t12; |
| t3 += z1 + t13; |
| |
| <span class="kw">let </span>z1 = (t1 + t2) * (-FIX_2_562915447); |
| <span class="kw">let </span><span class="kw-2">mut </span>t1 = t1 * FIX_3_072711026; |
| <span class="kw">let </span><span class="kw-2">mut </span>t2 = t2 * FIX_2_053119869; |
| t1 += z1 + t13; |
| t2 += z1 + t12; |
| |
| coeffs[x + <span class="number">8</span>] = t0 >> (CONST_BITS + PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[x + <span class="number">8 </span>* <span class="number">3</span>] = t1 >> (CONST_BITS + PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[x + <span class="number">8 </span>* <span class="number">5</span>] = t2 >> (CONST_BITS + PASS1_BITS) <span class="kw">as </span>usize; |
| coeffs[x + <span class="number">8 </span>* <span class="number">7</span>] = t3 >> (CONST_BITS + PASS1_BITS) <span class="kw">as </span>usize; |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="image" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
