/** Create a color table from the image ColorModel and SampleModel. */
private static byte[] createColorTable(ColorModel colorModel, SampleModel sampleModel) {
byte[] colorTable;
if (colorModel instanceof IndexColorModel) {
IndexColorModel icm = (IndexColorModel) colorModel;
int mapSize = icm.getMapSize();
/**
* The GIF image format assumes that size of image palette is power of two. We will use
* closest larger power of two as size of color table.
*/
int ctSize = getGifPaletteSize(mapSize);
byte[] reds = new byte[ctSize];
byte[] greens = new byte[ctSize];
byte[] blues = new byte[ctSize];
icm.getReds(reds);
icm.getGreens(greens);
icm.getBlues(blues);
/**
* fill tail of color component arrays by replica of first color in order to avoid appearance
* of extra colors in the color table
*/
for (int i = mapSize; i < ctSize; i++) {
reds[i] = reds[0];
greens[i] = greens[0];
blues[i] = blues[0];
}
colorTable = new byte[3 * ctSize];
int idx = 0;
for (int i = 0; i < ctSize; i++) {
colorTable[idx++] = reds[i];
colorTable[idx++] = greens[i];
colorTable[idx++] = blues[i];
}
} else if (sampleModel.getNumBands() == 1) {
// create gray-scaled color table for single-banded images
int numBits = sampleModel.getSampleSize()[0];
if (numBits > 8) {
numBits = 8;
}
int colorTableLength = 3 * (1 << numBits);
colorTable = new byte[colorTableLength];
for (int i = 0; i < colorTableLength; i++) {
colorTable[i] = (byte) (i / 3);
}
} else {
// We do not have enough information here
// to create well-fit color table for RGB image.
colorTable = null;
}
return colorTable;
}
/**
* Writes any extension blocks, the Image Descriptor, the image data, and optionally the header
* (Signature and Logical Screen Descriptor) and trailer (Block Terminator).
*
* @param writeHeader Whether to write the header.
* @param writeTrailer Whether to write the trailer.
* @param sm The stream metadata or <code>null</code> if <code>writeHeader</code> is <code>false
* </code>.
* @param iioimage The image and image metadata.
* @param p The write parameters.
* @throws IllegalArgumentException if the number of bands is not 1.
* @throws IllegalArgumentException if the number of bits per sample is greater than 8.
* @throws IllegalArgumentException if the color component size is greater than 8.
* @throws IllegalArgumentException if <code>writeHeader</code> is <code>true</code> and <code>sm
* </code> is <code>null</code>.
* @throws IllegalArgumentException if <code>writeHeader</code> is <code>false</code> and a
* sequence is not being written.
*/
private void write(
boolean writeHeader,
boolean writeTrailer,
IIOMetadata sm,
IIOImage iioimage,
ImageWriteParam p)
throws IOException {
clearAbortRequest();
RenderedImage image = iioimage.getRenderedImage();
// Check for ability to encode image.
if (needToCreateIndex(image)) {
image = PaletteBuilder.createIndexedImage(image);
iioimage.setRenderedImage(image);
}
ColorModel colorModel = image.getColorModel();
SampleModel sampleModel = image.getSampleModel();
// Determine source region and destination dimensions.
Rectangle sourceBounds =
new Rectangle(image.getMinX(), image.getMinY(), image.getWidth(), image.getHeight());
Dimension destSize = new Dimension();
computeRegions(sourceBounds, destSize, p);
// Convert any provided image metadata.
GIFWritableImageMetadata imageMetadata = null;
if (iioimage.getMetadata() != null) {
imageMetadata = new GIFWritableImageMetadata();
convertMetadata(IMAGE_METADATA_NAME, iioimage.getMetadata(), imageMetadata);
// Converted rgb image can use palette different from global.
// In order to avoid color artefacts we want to be sure we use
// appropriate palette. For this we initialize local color table
// from current color and sample models.
// At this point we can guarantee that local color table can be
// build because image was already converted to indexed or
// gray-scale representations
if (imageMetadata.localColorTable == null) {
imageMetadata.localColorTable = createColorTable(colorModel, sampleModel);
// in case of indexed image we should take care of
// transparent pixels
if (colorModel instanceof IndexColorModel) {
IndexColorModel icm = (IndexColorModel) colorModel;
int index = icm.getTransparentPixel();
imageMetadata.transparentColorFlag = (index != -1);
if (imageMetadata.transparentColorFlag) {
imageMetadata.transparentColorIndex = index;
}
/* NB: transparentColorFlag might have not beed reset for
greyscale images but explicitly reseting it here
is potentially not right thing to do until we have way
to find whether current value was explicitly set by
the user.
*/
}
}
}
// Global color table values.
byte[] globalColorTable = null;
// Write the header (Signature+Logical Screen Descriptor+
// Global Color Table).
if (writeHeader) {
if (sm == null) {
throw new IllegalArgumentException("Cannot write null header!");
}
GIFWritableStreamMetadata streamMetadata = (GIFWritableStreamMetadata) sm;
// Set the version if not set.
if (streamMetadata.version == null) {
streamMetadata.version = "89a";
}
// Set the Logical Screen Desriptor if not set.
if (streamMetadata.logicalScreenWidth == GIFMetadata.UNDEFINED_INTEGER_VALUE) {
streamMetadata.logicalScreenWidth = destSize.width;
}
if (streamMetadata.logicalScreenHeight == GIFMetadata.UNDEFINED_INTEGER_VALUE) {
streamMetadata.logicalScreenHeight = destSize.height;
}
if (streamMetadata.colorResolution == GIFMetadata.UNDEFINED_INTEGER_VALUE) {
streamMetadata.colorResolution =
colorModel != null ? colorModel.getComponentSize()[0] : sampleModel.getSampleSize()[0];
}
// Set the Global Color Table if not set, i.e., if not
// provided in the stream metadata.
if (streamMetadata.globalColorTable == null) {
if (isWritingSequence && imageMetadata != null && imageMetadata.localColorTable != null) {
// Writing a sequence and a local color table was
// provided in the metadata of the first image: use it.
streamMetadata.globalColorTable = imageMetadata.localColorTable;
} else if (imageMetadata == null || imageMetadata.localColorTable == null) {
// Create a color table.
streamMetadata.globalColorTable = createColorTable(colorModel, sampleModel);
}
}
// Set the Global Color Table. At this point it should be
// A) the global color table provided in stream metadata, if any;
// B) the local color table of the image metadata, if any, if
// writing a sequence;
// C) a table created on the basis of the first image ColorModel
// and SampleModel if no local color table is available; or
// D) null if none of the foregoing conditions obtain (which
// should only be if a sequence is not being written and
// a local color table is provided in image metadata).
globalColorTable = streamMetadata.globalColorTable;
// Write the header.
int bitsPerPixel;
if (globalColorTable != null) {
bitsPerPixel = getNumBits(globalColorTable.length / 3);
} else if (imageMetadata != null && imageMetadata.localColorTable != null) {
bitsPerPixel = getNumBits(imageMetadata.localColorTable.length / 3);
} else {
bitsPerPixel = sampleModel.getSampleSize(0);
}
writeHeader(streamMetadata, bitsPerPixel);
} else if (isWritingSequence) {
globalColorTable = theStreamMetadata.globalColorTable;
} else {
throw new IllegalArgumentException("Must write header for single image!");
}
// Write extension blocks, Image Descriptor, and image data.
writeImage(
iioimage.getRenderedImage(), imageMetadata, p, globalColorTable, sourceBounds, destSize);
// Write the trailer.
if (writeTrailer) {
writeTrailer();
}
}