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comparison dwt/internal/image/PngTrnsChunk.d @ 0:380af2bdd8e5

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author Jacob Carlborg <doob@me.com> <jacob.carlborg@gmail.com>
date Sat, 09 Aug 2008 17:00:02 +0200
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children 1a8b3cb347e0
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-1:000000000000 0:380af2bdd8e5
1 /*******************************************************************************
2 * Copyright (c) 2000, 2006 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM Corporation - initial API and implementation
10 *******************************************************************************/
11 module dwt.internal.image;
12
13
14 import dwt.DWT;
15 import dwt.graphics.RGB;
16
17 public class PngTrnsChunk : PngChunk {
18 static final int TRANSPARENCY_TYPE_PIXEL = 0;
19 static final int TRANSPARENCY_TYPE_ALPHAS = 1;
20 static final int RGB_DATA_LENGTH = 6;
21
22 PngTrnsChunk(RGB rgb) {
23 super(RGB_DATA_LENGTH);
24 setType(TYPE_tRNS);
25 setInt16(DATA_OFFSET, rgb.red);
26 setInt16(DATA_OFFSET + 2, rgb.green);
27 setInt16(DATA_OFFSET + 4, rgb.blue);
28 setCRC(computeCRC());
29 }
30
31 PngTrnsChunk(byte[] reference){
32 super(reference);
33 }
34
35 int getChunkType() {
36 return CHUNK_tRNS;
37 }
38
39 void validateLength(PngIhdrChunk header, PngPlteChunk paletteChunk) {
40 bool valid;
41 switch (header.getColorType()) {
42 case PngIhdrChunk.COLOR_TYPE_RGB:
43 // Three 2-byte values (RGB)
44 valid = getLength() is 6;
45 break;
46 case PngIhdrChunk.COLOR_TYPE_PALETTE:
47 // Three 2-byte values (RGB)
48 valid = getLength() <= paletteChunk.getLength();
49 break;
50 case PngIhdrChunk.COLOR_TYPE_GRAYSCALE:
51 // One 2-byte value
52 valid = getLength() is 2;
53 break;
54 // Cannot use both Alpha and tRNS
55 case PngIhdrChunk.COLOR_TYPE_RGB_WITH_ALPHA:
56 case PngIhdrChunk.COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
57 default:
58 valid = false;
59 }
60 if (!valid) {
61 DWT.error(DWT.ERROR_INVALID_IMAGE);
62 }
63 }
64
65 /**
66 * Answer whether the chunk is a valid tRNS chunk.
67 */
68 void validate(PngFileReadState readState, PngIhdrChunk headerChunk, PngPlteChunk paletteChunk) {
69 if (!readState.readIHDR
70 || (headerChunk.getMustHavePalette() && !readState.readPLTE)
71 || readState.readIDAT
72 || readState.readIEND)
73 {
74 DWT.error(DWT.ERROR_INVALID_IMAGE);
75 } else {
76 readState.readTRNS = true;
77 }
78
79 validateLength(headerChunk, paletteChunk);
80
81 super.validate(readState, headerChunk);
82 }
83
84
85 int getTransparencyType(PngIhdrChunk header) {
86 if (header.getColorType() is PngIhdrChunk.COLOR_TYPE_PALETTE) {
87 return TRANSPARENCY_TYPE_ALPHAS;
88 }
89 return TRANSPARENCY_TYPE_PIXEL;
90 }
91
92 /**
93 * Answer the transparent pixel RGB value.
94 * This is not valid for palette color types.
95 * This is not valid for alpha color types.
96 * This will convert a grayscale value into
97 * a palette index.
98 * It will compress a 6 byte RGB into a 3 byte
99 * RGB.
100 */
101 int getSwtTransparentPixel(PngIhdrChunk header) {
102 switch (header.getColorType()) {
103 case PngIhdrChunk.COLOR_TYPE_GRAYSCALE:
104 int gray = ((reference[DATA_OFFSET] & 0xFF) << 8)
105 + (reference[DATA_OFFSET + 1] & 0xFF);
106 if (header.getBitDepth() > 8) {
107 return PNGFileFormat.compress16BitDepthTo8BitDepth(gray);
108 }
109 return gray & 0xFF;
110 case PngIhdrChunk.COLOR_TYPE_RGB:
111 int red = ((reference[DATA_OFFSET] & 0xFF) << 8)
112 | (reference[DATA_OFFSET + 1] & 0xFF);
113 int green = ((reference[DATA_OFFSET + 2] & 0xFF) << 8)
114 | (reference[DATA_OFFSET + 3] & 0xFF);
115 int blue = ((reference[DATA_OFFSET + 4] & 0xFF) << 8)
116 | (reference[DATA_OFFSET + 5] & 0xFF);
117 if (header.getBitDepth() > 8) {
118 red = PNGFileFormat.compress16BitDepthTo8BitDepth(red);
119 green = PNGFileFormat.compress16BitDepthTo8BitDepth(green);
120 blue = PNGFileFormat.compress16BitDepthTo8BitDepth(blue);
121 }
122 return (red << 16) | (green << 8) | blue;
123 default:
124 DWT.error(DWT.ERROR_INVALID_IMAGE);
125 return -1;
126 }
127 }
128
129 /**
130 * Answer an array of Alpha values that correspond to the
131 * colors in the palette.
132 * This is only valid for the COLOR_TYPE_PALETTE color type.
133 */
134 byte[] getAlphaValues(PngIhdrChunk header, PngPlteChunk paletteChunk) {
135 if (header.getColorType() !is PngIhdrChunk.COLOR_TYPE_PALETTE) {
136 DWT.error(DWT.ERROR_INVALID_IMAGE);
137 }
138 byte[] alphas = new byte[paletteChunk.getPaletteSize()];
139 int dataLength = getLength();
140 int i = 0;
141 for (i = 0; i < dataLength; i++) {
142 alphas[i] = reference[DATA_OFFSET + i];
143 }
144 /**
145 * Any palette entries which do not have a corresponding
146 * alpha value in the tRNS chunk are spec'd to have an
147 * alpha of 255.
148 */
149 for (int j = i; j < alphas.length; j++) {
150 alphas[j] = (byte) 255;
151 }
152 return alphas;
153 }
154 }