pngihdrchunk.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, 2004 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 org.eclipse.swt.internal.Compatibility;

class PngIhdrChunk extends PngChunk {
	static final int EXPECTED_DATA_LENGTH = 13;
	
	static final int WIDTH_DATA_OFFSET = DATA_OFFSET + 0;
	static final int HEIGHT_DATA_OFFSET = DATA_OFFSET + 4;
	static final int BIT_DEPTH_OFFSET = DATA_OFFSET + 8;
	static final int COLOR_TYPE_OFFSET = DATA_OFFSET + 9;
	static final int COMPRESSION_METHOD_OFFSET = DATA_OFFSET + 10;
	static final int FILTER_METHOD_OFFSET = DATA_OFFSET + 11;
	static final int INTERLACE_METHOD_OFFSET = DATA_OFFSET + 12;
	
	static final int COLOR_TYPE_GRAYSCALE = 0;
	static final int COLOR_TYPE_RGB = 2;
	static final int COLOR_TYPE_PALETTE = 3;
	static final int COLOR_TYPE_GRAYSCALE_WITH_ALPHA = 4;
	static final int COLOR_TYPE_RGB_WITH_ALPHA = 6;
	
	static final int INTERLACE_METHOD_NONE = 0;
	static final int INTERLACE_METHOD_ADAM7 = 1;
	
	static final int FILTER_NONE = 0;
	static final int FILTER_SUB = 1;
	static final int FILTER_UP = 2;
	static final int FILTER_AVERAGE = 3;
	static final int FILTER_PAETH = 4;
	
	static final byte[] ValidBitDepths = {1, 2, 4, 8, 16};
	static final byte[] ValidColorTypes = {0, 2, 3, 4, 6};
	
/**
 * Construct a PNGChunk using the reference bytes
 * given.
 */	
PngIhdrChunk(byte[] reference) {
	super(reference);
}

/**
 * Get the image's width in pixels.
 */
int getWidth() {
	return getInt32(WIDTH_DATA_OFFSET);
}

/**
 * Set the image's width in pixels.
 */
void setWidth(int value) {
	setInt32(WIDTH_DATA_OFFSET, value);
}

/**
 * Get the image's height in pixels.
 */
int getHeight() {
	return getInt32(HEIGHT_DATA_OFFSET);
}

/**
 * Set the image's height in pixels.
 */
void setHeight(int value) {
	setInt32(HEIGHT_DATA_OFFSET, value);
}

/**
 * Get the image's bit depth.
 * This is limited to the values 1, 2, 4, 8, or 16.
 */
byte getBitDepth() {
	return reference[BIT_DEPTH_OFFSET];
}

/**
 * Set the image's bit depth.
 * This is limited to the values 1, 2, 4, 8, or 16.
 */
void setBitDepth(byte value) {
	reference[BIT_DEPTH_OFFSET] = value;
}

/**
 * Get the image's color type.
 * This is limited to the values:
 * 0 - Grayscale image.
 * 2 - RGB triple.
 * 3 - Palette.
 * 4 - Grayscale with Alpha channel.
 * 6 - RGB with Alpha channel.
 */
byte getColorType() {
	return reference[COLOR_TYPE_OFFSET];
}

/**
 * Set the image's color type.
 * This is limited to the values:
 * 0 - Grayscale image.
 * 2 - RGB triple.
 * 3 - Palette.
 * 4 - Grayscale with Alpha channel.
 * 6 - RGB with Alpha channel.
 */
void setColorType(byte value) {
	reference[COLOR_TYPE_OFFSET] = value;
}

/**
 * Get the image's compression method.
 * This value must be 0.
 */
byte getCompressionMethod() {
	return reference[COMPRESSION_METHOD_OFFSET];
}

/**
 * Set the image's compression method.
 * This value must be 0.
 */
void setCompressionMethod(byte value) {
	reference[COMPRESSION_METHOD_OFFSET] = value;
}

/**
 * Get the image's filter method.
 * This value must be 0.
 */
byte getFilterMethod() {
	return reference[FILTER_METHOD_OFFSET];
}

/**
 * Set the image's filter method.
 * This value must be 0.
 */
void setFilterMethod(byte value) {
	reference[FILTER_METHOD_OFFSET] = value;
}

/**
 * Get the image's interlace method.
 * This value is limited to:
 * 0 - No interlacing used.
 * 1 - Adam7 interlacing used.
 */
byte getInterlaceMethod() {
	return reference[INTERLACE_METHOD_OFFSET];
}

/**
 * Set the image's interlace method.
 * This value is limited to:
 * 0 - No interlacing used.
 * 1 - Adam7 interlacing used.
 */
void setInterlaceMethod(byte value) {
	reference[INTERLACE_METHOD_OFFSET] = value;
}

/**
 * Answer whether the chunk is a valid IHDR chunk.
 */
void validate(PngFileReadState readState, PngIhdrChunk headerChunk) {
	// An IHDR chunk is invalid if any other chunk has
	// been read.
	if (readState.readIHDR 
		|| readState.readPLTE
		|| readState.readIDAT
		|| readState.readIEND) 
	{
		SWT.error(SWT.ERROR_INVALID_IMAGE);
	} else {
		readState.readIHDR = true;
	}
	
	super.validate(readState, headerChunk);
	
	if (getLength() != EXPECTED_DATA_LENGTH) SWT.error(SWT.ERROR_INVALID_IMAGE);
	if (getCompressionMethod() != 0) SWT.error(SWT.ERROR_INVALID_IMAGE);
	if (getInterlaceMethod() != INTERLACE_METHOD_NONE &&
		getInterlaceMethod() != INTERLACE_METHOD_ADAM7) {
			SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	
	boolean colorTypeIsValid = false;
	byte colorType = getColorType();
	for (int i = 0; i < ValidColorTypes.length; i++) {
		if (ValidColorTypes[i] == colorType) {
			colorTypeIsValid = true;
			break;
		}
	}
	if (!colorTypeIsValid) SWT.error(SWT.ERROR_INVALID_IMAGE);

	boolean bitDepthIsValid = false;
	byte bitDepth = getBitDepth();
	for (int i = 0; i < ValidBitDepths.length; i++) {
		if (ValidBitDepths[i] == bitDepth) {
			bitDepthIsValid = true;
			break;
		}
	}
	if (!bitDepthIsValid) SWT.error(SWT.ERROR_INVALID_IMAGE);
	
	if ((colorType == COLOR_TYPE_RGB 
		|| colorType == COLOR_TYPE_RGB_WITH_ALPHA
		|| colorType == COLOR_TYPE_GRAYSCALE_WITH_ALPHA)
		&& bitDepth < 8) 
	{
			SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	
	if (colorType == COLOR_TYPE_PALETTE && bitDepth > 8) {
		SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
}

String getColorTypeString() {
	switch (getColorType()) {
		case COLOR_TYPE_GRAYSCALE: 				return "Grayscale";
		case COLOR_TYPE_RGB: 					return "RGB";		
		case COLOR_TYPE_PALETTE:				return "Palette";
		case COLOR_TYPE_GRAYSCALE_WITH_ALPHA:	return "Grayscale with Alpha";
		case COLOR_TYPE_RGB_WITH_ALPHA:			return "RGB with Alpha";
		default:								return "Unknown - " + getColorType();
	}
}

String getFilterMethodString() {
	switch (getFilterMethod()) {
		case FILTER_NONE:		return "None";
		case FILTER_SUB:		return "Sub";
		case FILTER_UP:			return "Up";
		case FILTER_AVERAGE:	return "Average";
		case FILTER_PAETH:		return "Paeth";
		default:				return "Unknown";
	}
}

String getInterlaceMethodString() {
	switch (getInterlaceMethod()) {
		case INTERLACE_METHOD_NONE: 	return "Not Interlaced";
		case INTERLACE_METHOD_ADAM7:	return "Interlaced - ADAM7";
		default:				return "Unknown";
	}
}

void contributeToString(StringBuffer buffer) {
	buffer.append("\n\tWidth: ");
	buffer.append(getWidth());
	buffer.append("\n\tHeight: ");
	buffer.append(getHeight());
	buffer.append("\n\tBit Depth: ");
	buffer.append(getBitDepth());
	buffer.append("\n\tColor Type: ");
	buffer.append(getColorTypeString());
	buffer.append("\n\tCompression Method: ");
	buffer.append(getCompressionMethod());
	buffer.append("\n\tFilter Method: ");
	buffer.append(getFilterMethodString());
	buffer.append("\n\tInterlace Method: ");
	buffer.append(getInterlaceMethodString());
}

boolean getMustHavePalette() {
	return getColorType() == COLOR_TYPE_PALETTE;
}

boolean getCanHavePalette() {
	int colorType = getColorType();
	return colorType != COLOR_TYPE_GRAYSCALE && 
		colorType != COLOR_TYPE_GRAYSCALE_WITH_ALPHA;
}

/**
 * Answer the pixel size in bits based on the color type
 * and bit depth.
 */
int getBitsPerPixel() {
	int bitDepth = getBitDepth();
	switch (getColorType()) {
		case COLOR_TYPE_RGB_WITH_ALPHA:
			return 4 * bitDepth;
		case COLOR_TYPE_RGB:
			return 3 * bitDepth;
		case COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
			return 2 * bitDepth;
		case COLOR_TYPE_GRAYSCALE:
		case COLOR_TYPE_PALETTE:
			return bitDepth;
		default:
			SWT.error(SWT.ERROR_INVALID_IMAGE);
			return 0;
	}
}

/**
 * Answer the pixel size in bits based on the color type
 * and bit depth.
 */
int getSwtBitsPerPixel() {
	int bitDepth = getBitDepth();
	switch (getColorType()) {
		case COLOR_TYPE_RGB_WITH_ALPHA:
		case COLOR_TYPE_RGB:
		case COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
			return 24;
		case COLOR_TYPE_GRAYSCALE:
		case COLOR_TYPE_PALETTE:
			return Math.min(bitDepth, 8);
		default:
			SWT.error(SWT.ERROR_INVALID_IMAGE);
			return 0;
	}
}

int getFilterByteOffset() {
	if (getBitDepth() < 8) return 1;
	return getBitsPerPixel() / 8;
}

boolean usesDirectColor() {
	switch (getColorType()) {
		case COLOR_TYPE_GRAYSCALE:
		case COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
		case COLOR_TYPE_RGB:
		case COLOR_TYPE_RGB_WITH_ALPHA:
			return true;
		default:
			return false;
	}
}

PaletteData createGrayscalePalette() {
	int bitDepth = Math.min(getBitDepth(), 8);
	int max = Compatibility.pow2(bitDepth) - 1;
	int delta = 255 / max;
	int gray = 0;
	RGB[] rgbs = new RGB[max + 1]; 
	for (int i = 0; i <= max; i++) {
		rgbs[i] = new RGB(gray, gray, gray);
		gray += delta;
	}
	return new PaletteData(rgbs);
}

PaletteData getPaletteData() {
	switch (getColorType()) {
		case COLOR_TYPE_GRAYSCALE:
			return createGrayscalePalette();
		case COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
		case COLOR_TYPE_RGB:
		case COLOR_TYPE_RGB_WITH_ALPHA:
			return new PaletteData(0xFF0000, 0xFF00, 0xFF);
		default:
			return null;
	}	
}



}