--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwt/internal/image/PngTrnsChunk.d	Sat Aug 09 17:00:02 2008 +0200
@@ -0,0 +1,154 @@
+/*******************************************************************************
+ * Copyright (c) 2000, 2006 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+module dwt.internal.image;
+
+
+import dwt.DWT;
+import dwt.graphics.RGB;
+
+public class PngTrnsChunk : PngChunk {
+    static final int TRANSPARENCY_TYPE_PIXEL = 0;
+    static final int TRANSPARENCY_TYPE_ALPHAS = 1;
+    static final int RGB_DATA_LENGTH = 6;
+    
+PngTrnsChunk(RGB rgb) {
+    super(RGB_DATA_LENGTH);
+    setType(TYPE_tRNS);
+    setInt16(DATA_OFFSET, rgb.red);
+    setInt16(DATA_OFFSET + 2, rgb.green);
+    setInt16(DATA_OFFSET + 4, rgb.blue);    
+    setCRC(computeCRC());
+}
+
+PngTrnsChunk(byte[] reference){
+    super(reference);
+}
+
+int getChunkType() {
+    return CHUNK_tRNS;
+}
+
+void validateLength(PngIhdrChunk header, PngPlteChunk paletteChunk) {
+    bool valid;
+    switch (header.getColorType()) {
+        case PngIhdrChunk.COLOR_TYPE_RGB:
+            // Three 2-byte values (RGB)
+            valid = getLength() is 6;
+            break;
+        case PngIhdrChunk.COLOR_TYPE_PALETTE:
+            // Three 2-byte values (RGB)
+            valid = getLength() <= paletteChunk.getLength();
+            break;
+        case PngIhdrChunk.COLOR_TYPE_GRAYSCALE:
+            // One 2-byte value
+            valid = getLength() is 2;
+            break;
+        // Cannot use both Alpha and tRNS
+        case PngIhdrChunk.COLOR_TYPE_RGB_WITH_ALPHA:
+        case PngIhdrChunk.COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
+        default:
+            valid = false;
+    }
+    if (!valid) {
+        DWT.error(DWT.ERROR_INVALID_IMAGE);
+    }
+}
+
+/**
+ * Answer whether the chunk is a valid tRNS chunk.
+ */
+void validate(PngFileReadState readState, PngIhdrChunk headerChunk, PngPlteChunk paletteChunk) {
+    if (!readState.readIHDR
+        || (headerChunk.getMustHavePalette() && !readState.readPLTE)
+        || readState.readIDAT
+        || readState.readIEND) 
+    {
+        DWT.error(DWT.ERROR_INVALID_IMAGE);
+    } else {
+        readState.readTRNS = true;
+    }
+    
+    validateLength(headerChunk, paletteChunk);
+    
+    super.validate(readState, headerChunk);
+}
+
+
+int getTransparencyType(PngIhdrChunk header) {
+    if (header.getColorType() is PngIhdrChunk.COLOR_TYPE_PALETTE) {
+        return TRANSPARENCY_TYPE_ALPHAS;
+    }
+    return TRANSPARENCY_TYPE_PIXEL;
+}
+
+/**
+ * Answer the transparent pixel RGB value.
+ * This is not valid for palette color types.
+ * This is not valid for alpha color types.
+ * This will convert a grayscale value into
+ * a palette index.
+ * It will compress a 6 byte RGB into a 3 byte
+ * RGB.
+ */
+int getSwtTransparentPixel(PngIhdrChunk header) {
+    switch (header.getColorType()) {
+        case PngIhdrChunk.COLOR_TYPE_GRAYSCALE:
+            int gray = ((reference[DATA_OFFSET] & 0xFF) << 8)
+                + (reference[DATA_OFFSET + 1] & 0xFF);
+            if (header.getBitDepth() > 8) {
+                return PNGFileFormat.compress16BitDepthTo8BitDepth(gray);
+            }
+            return gray & 0xFF;
+        case PngIhdrChunk.COLOR_TYPE_RGB:
+            int red = ((reference[DATA_OFFSET] & 0xFF) << 8)
+                | (reference[DATA_OFFSET + 1] & 0xFF);
+            int green = ((reference[DATA_OFFSET + 2] & 0xFF) << 8)
+                | (reference[DATA_OFFSET + 3] & 0xFF);
+            int blue = ((reference[DATA_OFFSET + 4] & 0xFF) << 8)
+                | (reference[DATA_OFFSET + 5] & 0xFF);          
+            if (header.getBitDepth() > 8) {
+                red = PNGFileFormat.compress16BitDepthTo8BitDepth(red);
+                green = PNGFileFormat.compress16BitDepthTo8BitDepth(green);
+                blue = PNGFileFormat.compress16BitDepthTo8BitDepth(blue);           
+            }
+            return (red << 16) | (green << 8) | blue;   
+        default:
+            DWT.error(DWT.ERROR_INVALID_IMAGE);
+            return -1;
+    }
+}
+
+/**
+ * Answer an array of Alpha values that correspond to the 
+ * colors in the palette.
+ * This is only valid for the COLOR_TYPE_PALETTE color type.
+ */
+byte[] getAlphaValues(PngIhdrChunk header, PngPlteChunk paletteChunk) {
+    if (header.getColorType() !is PngIhdrChunk.COLOR_TYPE_PALETTE) {
+        DWT.error(DWT.ERROR_INVALID_IMAGE);
+    }
+    byte[] alphas = new byte[paletteChunk.getPaletteSize()];
+    int dataLength = getLength();
+    int i = 0;
+    for (i = 0; i < dataLength; i++) {
+        alphas[i] = reference[DATA_OFFSET + i];
+    }
+    /**
+     * Any palette entries which do not have a corresponding
+     * alpha value in the tRNS chunk are spec'd to have an 
+     * alpha of 255.
+     */
+    for (int j = i; j < alphas.length; j++) {
+        alphas[j] = (byte) 255;
+    }
+    return alphas;
+}
+}