| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.sanselan.formats.png; |
| |
| import org.apache.commons.sanselan.ImageReadException; |
| |
| public class BitParser |
| { |
| private final byte bytes[]; |
| private final int bitsPerPixel; |
| private final int bitDepth; |
| |
| public BitParser(byte bytes[], int bitsPerPixel, int bitDepth) |
| { |
| this.bytes = bytes; |
| this.bitsPerPixel = bitsPerPixel; |
| this.bitDepth = bitDepth; |
| } |
| |
| public int getSample(int pixelIndexInScanline, int sampleIndex) |
| throws ImageReadException |
| { |
| int pixelIndexBits = bitsPerPixel * pixelIndexInScanline; |
| int sampleIndexBits = pixelIndexBits + (sampleIndex * bitDepth); |
| int sampleIndexBytes = sampleIndexBits >> 3; |
| |
| if (bitDepth == 8) |
| return 0xff & bytes[sampleIndexBytes]; |
| else if (bitDepth < 8) |
| { |
| int b = 0xff & bytes[sampleIndexBytes]; |
| int bitsToShift = 8 - ((pixelIndexBits & 7) + bitDepth); |
| b >>= bitsToShift; |
| |
| int bitmask = (1 << bitDepth) - 1; |
| return b & bitmask; |
| } else if (bitDepth == 16) |
| { |
| return (((0xff & bytes[sampleIndexBytes]) << 8) | (0xff & bytes[sampleIndexBytes + 1])); |
| } |
| |
| throw new ImageReadException("PNG: bad BitDepth: " + bitDepth); |
| } |
| |
| public int getSampleAsByte(int pixelIndexInScanline, int sampleIndex) |
| throws ImageReadException |
| { |
| int sample = getSample(pixelIndexInScanline, sampleIndex); |
| |
| int rot = 8 - bitDepth; |
| if (rot > 0) |
| sample = sample * 255 / ((1 << bitDepth) - 1); |
| else if (rot < 0) |
| sample >>= -rot; |
| |
| return 0xff & sample; |
| } |
| } |