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TIFFNullDecompressor.java
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/
TIFFNullDecompressor.java
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/*
* Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.sun.imageio.plugins.tiff;
import java.io.EOFException;
import java.io.IOException;
public class TIFFNullDecompressor extends TIFFDecompressor {
/**
* Whether to read the active source region only.
*/
private boolean isReadActiveOnly = false;
/** The original value of {@code srcMinX}. */
private int originalSrcMinX;
/** The original value of {@code srcMinY}. */
private int originalSrcMinY;
/** The original value of {@code srcWidth}. */
private int originalSrcWidth;
/** The original value of {@code srcHeight}. */
private int originalSrcHeight;
public TIFFNullDecompressor() {}
//
// This approach to reading the active region is a not the best
// as the original values of the entire source region are stored,
// overwritten, and then restored. It would probably be better to
// revise TIFFDecompressor such that this were not necessary, i.e.,
// change beginDecoding() and decode() to use the active region values
// when random access is easy and the entire region values otherwise.
//
public void beginDecoding() {
// Determine number of bits per pixel.
int bitsPerPixel = 0;
for(int i = 0; i < bitsPerSample.length; i++) {
bitsPerPixel += bitsPerSample[i];
}
// Can read active region only if row starts on a byte boundary.
if((activeSrcMinX != srcMinX || activeSrcMinY != srcMinY ||
activeSrcWidth != srcWidth || activeSrcHeight != srcHeight) &&
((activeSrcMinX - srcMinX)*bitsPerPixel) % 8 == 0) {
// Set flag.
isReadActiveOnly = true;
// Cache original region.
originalSrcMinX = srcMinX;
originalSrcMinY = srcMinY;
originalSrcWidth = srcWidth;
originalSrcHeight = srcHeight;
// Replace region with active region.
srcMinX = activeSrcMinX;
srcMinY = activeSrcMinY;
srcWidth = activeSrcWidth;
srcHeight = activeSrcHeight;
} else {
// Clear flag.
isReadActiveOnly = false;
}
super.beginDecoding();
}
public void decode() throws IOException {
super.decode();
// Reset state.
if(isReadActiveOnly) {
// Restore original source region values.
srcMinX = originalSrcMinX;
srcMinY = originalSrcMinY;
srcWidth = originalSrcWidth;
srcHeight = originalSrcHeight;
// Unset flag.
isReadActiveOnly = false;
}
}
public void decodeRaw(byte[] b,
int dstOffset,
int bitsPerPixel,
int scanlineStride) throws IOException {
if(isReadActiveOnly) {
// Read the active source region only.
int activeBytesPerRow = (activeSrcWidth*bitsPerPixel + 7)/8;
int totalBytesPerRow = (originalSrcWidth*bitsPerPixel + 7)/8;
int bytesToSkipPerRow = totalBytesPerRow - activeBytesPerRow;
//
// Seek to the start of the active region:
//
// active offset = original offset +
// number of bytes to start of first active row +
// number of bytes to first active pixel within row
//
// Since the condition for reading from the active region only is
//
// ((activeSrcMinX - srcMinX)*bitsPerPixel) % 8 == 0
//
// the bit offset to the first active pixel within the first
// active row is a multiple of 8.
//
stream.seek(offset +
(activeSrcMinY - originalSrcMinY)*totalBytesPerRow +
((activeSrcMinX - originalSrcMinX)*bitsPerPixel)/8);
int lastRow = activeSrcHeight - 1;
for (int y = 0; y < activeSrcHeight; y++) {
stream.readFully(b, dstOffset, activeBytesPerRow);
dstOffset += scanlineStride;
// Skip unneeded bytes (row suffix + row prefix).
if(y != lastRow) {
stream.skipBytes(bytesToSkipPerRow);
}
}
} else {
// Read the entire source region.
stream.seek(offset);
int bytesPerRow = (srcWidth*bitsPerPixel + 7)/8;
if(bytesPerRow == scanlineStride) {
stream.readFully(b, dstOffset, bytesPerRow*srcHeight);
} else {
for (int y = 0; y < srcHeight; y++) {
stream.readFully(b, dstOffset, bytesPerRow);
dstOffset += scanlineStride;
}
}
}
}
}