tiffdirectory.java

源码为Eclipse开源开发平台桌面开发工具SWT的源代码,

/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.internal.image;


import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import java.io.*;

final class TIFFDirectory {

	TIFFRandomFileAccess file;
	boolean isLittleEndian;
	ImageLoader loader;
	int depth;
	
	/* Directory fields */
	int imageWidth;
	int imageLength;
	int[] bitsPerSample;
	int compression;
	int photometricInterpretation;
	int[] stripOffsets;
	int samplesPerPixel;
	int rowsPerStrip;
	int[] stripByteCounts;
	int t4Options;
	int colorMapOffset;
	
	/* Encoder fields */
	ImageData image;
	LEDataOutputStream out;
	
	static final int NO_VALUE = -1;
	
	static final short TAG_ImageWidth = 256;
	static final short TAG_ImageLength = 257;
	static final short TAG_BitsPerSample = 258;
	static final short TAG_Compression = 259;
	static final short TAG_PhotometricInterpretation = 262;
	static final short TAG_StripOffsets = 273;
	static final short TAG_SamplesPerPixel = 277;
	static final short TAG_RowsPerStrip = 278;
	static final short TAG_StripByteCounts = 279;
	static final short TAG_XResolution = 282;
	static final short TAG_YResolution = 283;
	static final short TAG_T4Options = 292;
	static final short TAG_ResolutionUnit = 296;
	static final short TAG_ColorMap = 320;
	
	static final int TYPE_BYTE = 1;
	static final int TYPE_ASCII = 2;
	static final int TYPE_SHORT = 3;
	static final int TYPE_LONG = 4;
	static final int TYPE_RATIONAL = 5;
	
	/* Different compression schemes */
	static final int COMPRESSION_NONE = 1;
	static final int COMPRESSION_CCITT_3_1 = 2;
	static final int COMPRESSION_PACKBITS = 32773;
	
	static final int IFD_ENTRY_SIZE = 12;
	
public TIFFDirectory(TIFFRandomFileAccess file, boolean isLittleEndian, ImageLoader loader) {
	this.file = file;
	this.isLittleEndian = isLittleEndian;
	this.loader = loader;
}

public TIFFDirectory(ImageData image) {
	this.image = image;
}

/* PackBits decoder */
int decodePackBits(byte[] src, byte[] dest, int offsetDest) {
	int destIndex = offsetDest;
	int srcIndex = 0;
	while (srcIndex < src.length) {
		byte n = src[srcIndex];
		if (0 <= n && n <= 127) {
			/* Copy next n+1 bytes literally */
			System.arraycopy(src, ++srcIndex, dest, destIndex, n + 1);
			srcIndex += n + 1;		
			destIndex += n + 1;	
		} else if (-127 <= n && n <= -1) {
			/* Copy next byte -n+1 times */
			byte value = src[++srcIndex];
			for (int j = 0; j < -n + 1; j++) {
				dest[destIndex++] = value;
			}
			srcIndex++;
		} else {
			/* Noop when n == -128 */
			srcIndex++;
		}
	}
	/* Number of bytes copied */
	return destIndex - offsetDest;
}

int getEntryValue(int type, byte[] buffer, int index) {
	return toInt(buffer, index + 8, type);
}

void getEntryValue(int type, byte[] buffer, int index, int[] values) throws IOException {
	int start = index + 8;
	int size;
	int offset = toInt(buffer, start, TYPE_LONG);
	switch (type) {
		case TYPE_SHORT: size = 2; break;
		case TYPE_LONG: size = 4; break; 
		case TYPE_RATIONAL: size = 8; break;
		case TYPE_ASCII:
		case TYPE_BYTE: size = 1; break;
		default: SWT.error(SWT.ERROR_UNSUPPORTED_FORMAT); return;
	}
	if (values.length * size > 4) {
		buffer = new byte[values.length * size]; 
		file.seek(offset);
		file.read(buffer);
		start = 0;
	}
	for (int i = 0; i < values.length; i++) {
		values[i] = toInt(buffer, start + i * size, type);
	}
}

void decodePixels(ImageData image) throws IOException {
	/* Each row is byte aligned */ 
	byte[] imageData = new byte[(imageWidth * depth + 7) / 8 * imageLength];
	image.data = imageData;
	int destIndex = 0;
	int length = stripOffsets.length;
	for (int i = 0; i < length; i++) {
		/* Read a strip */
		byte[] data = new byte[stripByteCounts[i]];
		file.seek(stripOffsets[i]);
		file.read(data);
		if (compression == COMPRESSION_NONE) {
			System.arraycopy(data, 0, imageData, destIndex, data.length);
			destIndex += data.length;
		} else if (compression == COMPRESSION_PACKBITS) {
			destIndex += decodePackBits(data, imageData, destIndex);
		} else if (compression == COMPRESSION_CCITT_3_1 || compression == 3) {
			TIFFModifiedHuffmanCodec codec = new TIFFModifiedHuffmanCodec();
			int nRows = rowsPerStrip;
			if (i == length -1) {
				int n = imageLength % rowsPerStrip;
				if (n != 0) nRows = n;
			}
			destIndex += codec.decode(data, imageData, destIndex, imageWidth, nRows);
		}
		if (loader.hasListeners()) {
			loader.notifyListeners(new ImageLoaderEvent(loader, image, i, i == length - 1));
		}
	}
}

PaletteData getColorMap() throws IOException {
	int numColors = 1 << bitsPerSample[0];
	/* R, G, B entries are 16 bit wide (2 bytes) */
	int numBytes = 3 * 2 * numColors;
	byte[] buffer = new byte[numBytes];
	file.seek(colorMapOffset);
	file.read(buffer);
	RGB[] colors = new RGB[numColors];
	/**
	 * SWT does not support 16-bit depth color formats.
	 * Convert the 16-bit data to 8-bit data.
	 * The correct way to do this is to multiply each
	 * 16 bit value by the value:
	 * (2^8 - 1) / (2^16 - 1).
	 * The fast way to do this is just to drop the low
	 * byte of the 16-bit value.
	 */
	int offset = isLittleEndian ? 1 : 0;
	int startG = 2 * numColors;
	int startB = startG + 2 * numColors;
	for (int i = 0; i < numColors; i++) {
		int r = buffer[offset] & 0xFF;
		int g = buffer[startG + offset] & 0xFF;
		int b = buffer[startB + offset] & 0xFF;
		colors[i] = new RGB(r, g, b);
		offset += 2;
	}
	return new PaletteData(colors);
}

PaletteData getGrayPalette() {
	int numColors = 1 << bitsPerSample[0];
	RGB[] rgbs = new RGB[numColors];
	for (int i = 0; i < numColors; i++) {
		int value = i * 0xFF / (numColors - 1);
		if (photometricInterpretation == 0) value = 0xFF - value;
		rgbs[i] = new RGB(value, value, value);
	}
	return new PaletteData(rgbs);
}

PaletteData getRGBPalette(int bitsR, int bitsG, int bitsB) {	
	int blueMask = 0;
	for (int i = 0; i < bitsB; i++) {
		blueMask |= 1 << i;
	}
	int greenMask = 0;
	for (int i = bitsB; i < bitsB + bitsG; i++) {
		greenMask |= 1 << i;
	}
	int redMask = 0;
	for (int i = bitsB + bitsG; i < bitsB + bitsG + bitsR; i++) {
		redMask |= 1 << i;
	}	
	return new PaletteData(redMask, greenMask, blueMask);
}

int formatStrips(int rowByteSize, int nbrRows, byte[] data, int maxStripByteSize, int offsetPostIFD, int extraBytes, int[][] strips) {
	/* 
	* Calculate the nbr of required strips given the following requirements: 
	* - each strip should, if possible, not be greater than maxStripByteSize
	* - each strip should contain 1 or more entire rows
	* 
	* Format the strip fields arrays so that the image data is stored in one
	* contiguous block. This block is stored after the IFD and after any tag
	* info described in the IFD.
	*/
	int n, nbrRowsPerStrip;
	if (rowByteSize > maxStripByteSize) {
		/* Each strip contains 1 row */
		n = data.length / rowByteSize;
		nbrRowsPerStrip = 1;
	} else {
		int nbr = (data.length + maxStripByteSize - 1) / maxStripByteSize;
		nbrRowsPerStrip = nbrRows / nbr;
		n = (nbrRows + nbrRowsPerStrip - 1) / nbrRowsPerStrip;	
	}
	int stripByteSize = rowByteSize * nbrRowsPerStrip;

	int[] offsets = new int[n];
	int[] counts = new int[n];
	/* 
	* Nbr of bytes between the end of the IFD directory and the start of
	* the image data. Keep space for at least the offsets and counts
	* data, each field being TYPE_LONG (4 bytes). If other tags require
	* space between the IFD and the image block, use the extraBytes
	* parameter.
	* If there is only one strip, the offsets and counts data is stored
	* directly in the IFD and we need not reserve space for it.
	*/
	int postIFDData = n == 1 ? 0 : n * 2 * 4;
	int startOffset = offsetPostIFD + extraBytes + postIFDData; /* offset of image data */
	
	int offset = startOffset;
	for (int i = 0; i < n; i++) {
		/* 
		* Store all strips sequentially to allow us
		* to copy all pixels in one contiguous area.
		*/
		offsets[i] = offset;
		counts[i] = stripByteSize;
		offset += stripByteSize;
	}
	/* The last strip may contain fewer rows */
	int mod = data.length % stripByteSize;
	if (mod != 0) counts[counts.length - 1] = mod;
	
	strips[0] = offsets;
	strips[1] = counts;
	return nbrRowsPerStrip;
}

int[] formatColorMap(RGB[] rgbs) {
	/* 
	* In a TIFF ColorMap, all red come first, followed by
	* green and blue. All values must be converted from
	* 8 bit to 16 bit. 
	*/
	int[] colorMap = new int[rgbs.length * 3];
	int offsetGreen = rgbs.length;
	int offsetBlue = rgbs.length * 2;
	for (int i = 0; i < rgbs.length; i++) {
		colorMap[i] = rgbs[i].red << 8 | rgbs[i].red;
		colorMap[i + offsetGreen] = rgbs[i].green << 8 | rgbs[i].green;
		colorMap[i + offsetBlue] = rgbs[i].blue << 8 | rgbs[i].blue;
	}
	return colorMap;
}

void parseEntries(byte[] buffer) throws IOException {
	for (int offset = 0; offset < buffer.length; offset += IFD_ENTRY_SIZE) {
		int tag = toInt(buffer, offset, TYPE_SHORT);
		int type = toInt(buffer, offset + 2, TYPE_SHORT);
		int count = toInt(buffer, offset + 4, TYPE_LONG);
		switch (tag) {
			case TAG_ImageWidth: {
				imageWidth = getEntryValue(type, buffer, offset);
				break;
			}
			case TAG_ImageLength: {
				imageLength = getEntryValue(type, buffer, offset);
				break;
			}
			case TAG_BitsPerSample: {
				if (type != TYPE_SHORT) SWT.error(SWT.ERROR_INVALID_IMAGE);
				bitsPerSample = new int[count];
				getEntryValue(type, buffer, offset, bitsPerSample);