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#399 Rewritten getSourceCSType to mimic libjpeg
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Harald Kuhr
parent
cdb2d72f8b
commit
3a86bfab98
@ -536,131 +536,86 @@ public final class JPEGImageReader extends ImageReaderBase {
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return image;
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}
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static JPEGColorSpace getSourceCSType(JFIF jfif, AdobeDCT adobeDCT, final Frame startOfFrame) throws IIOException {
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/*
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ADAPTED from http://download.oracle.com/javase/6/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html:
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When reading, the contents of the stream are interpreted by the usual JPEG conventions, as follows:
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• If a JFIF APP0 marker segment is present, the colorspace should be either grayscale or YCbCr.
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If an APP2 marker segment containing an embedded ICC profile is also present, then YCbCr is converted to RGB according
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to the formulas given in the JFIF spec, and the ICC profile is assumed to refer to the resulting RGB space.
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But, as software does not follow the spec, we can't really assume anything.
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• If an Adobe APP14 marker segment is present, the colorspace is determined by consulting the transform flag.
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The transform flag takes one of three values:
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o 2 - The image is encoded as YCCK (implicitly converted from CMYK on encoding).
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o 1 - The image is encoded as YCbCr (implicitly converted from RGB on encoding).
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o 0 - Unknown. 1-channel images are assumed to be Gray, 3-channel images are assumed to be RGB,
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4-channel images are assumed to be CMYK.
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• If neither marker segment is present, the following procedure is followed: Single-channel images are assumed
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to be grayscale, and 2-channel images are assumed to be grayscale with an alpha channel. For 3- and 4-channel
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images, the component ids are consulted. If these values are 1-3 for a 3-channel image, then the image is
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assumed to be YCbCr. If these values are 1-4 for a 4-channel image, then the image is assumed to be YCbCrA. If
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these values are > 4, they are checked against the ASCII codes for 'R', 'G', 'B', 'A', 'C', 'c', 'M', 'Y', 'K'.
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These can encode the following colorspaces:
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RGB
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RGBA
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YCC (as 'Y','C','c'), assumed to be PhotoYCC
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YCCA (as 'Y','C','c','A'), assumed to be PhotoYCCA
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CMYK (as 'C', 'M', 'Y', 'K').
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Otherwise, 3-channel subsampled images are assumed to be YCbCr, 3-channel non-subsampled images are assumed to
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be RGB, 4-channel subsampled images are assumed to be YCCK, and 4-channel, non-subsampled images are assumed to
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be CMYK.
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• All other images are declared uninterpretable and an exception is thrown if an attempt is made to read one as
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a BufferedImage. Such an image may be read only as a Raster. If an image is interpretable but there is no Java
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ColorSpace available corresponding to the encoded colorspace (e.g. YCbCr/YCCK), then ImageReader.getRawImageType
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will return null.
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*/
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if (adobeDCT != null) {
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switch (adobeDCT.transform) {
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case AdobeDCT.YCC:
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if (startOfFrame.componentsInFrame() != 3) {
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// This probably means the Adobe marker is bogus
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break;
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}
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return JPEGColorSpace.YCbCr;
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case AdobeDCT.YCCK:
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if (startOfFrame.componentsInFrame() != 4) {
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// This probably means the Adobe marker is bogus
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break;
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}
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return JPEGColorSpace.YCCK;
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case AdobeDCT.Unknown:
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if (startOfFrame.componentsInFrame() == 1) {
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return JPEGColorSpace.Gray;
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}
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else if (startOfFrame.componentsInFrame() == 3) {
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return JPEGColorSpace.RGB;
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}
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else if (startOfFrame.componentsInFrame() == 4) {
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return JPEGColorSpace.CMYK;
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}
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// Else fall through
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default:
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}
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}
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// TODO: We should probably allow component ids out of order (ie. BGR or KMCY)...
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private JPEGColorSpace getSourceCSType(final JFIF jfif, final AdobeDCT adobeDCT, final Frame startOfFrame) throws IIOException {
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// Adapted from libjpeg jdapimin.c:
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// Guess the input colorspace
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// (Wish JPEG committee had provided a real way to specify this...)
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switch (startOfFrame.componentsInFrame()) {
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case 1:
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return JPEGColorSpace.Gray;
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case 2:
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return JPEGColorSpace.GrayA;
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return JPEGColorSpace.GrayA; // Java special case: Gray + Alpha
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case 3:
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if (startOfFrame.components[0].id == 1 && startOfFrame.components[1].id == 2 && startOfFrame.components[2].id == 3) {
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// NOTE: Due to a bug in JPEGMetadata, standard format will report RGB for non-subsampled, non-JFIF files
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return JPEGColorSpace.YCbCr;
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if (jfif != null) {
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return JPEGColorSpace.YCbCr; // JFIF implies YCbCr
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}
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else if (startOfFrame.components[0].id == 'R' && startOfFrame.components[1].id == 'G' && startOfFrame.components[2].id == 'B') {
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return JPEGColorSpace.RGB;
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}
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else if (startOfFrame.components[0].id == 'Y' && startOfFrame.components[1].id == 'C' && startOfFrame.components[2].id == 'c') {
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return JPEGColorSpace.PhotoYCC;
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}
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else {
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// If subsampled, YCbCr else RGB
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for (Frame.Component component : startOfFrame.components) {
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if (component.hSub != 1 || component.vSub != 1) {
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else if (adobeDCT != null) {
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switch (adobeDCT.transform) {
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case AdobeDCT.Unknown:
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return JPEGColorSpace.RGB;
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case AdobeDCT.YCC:
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return JPEGColorSpace.YCbCr;
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}
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default:
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// TODO: Warning!
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return JPEGColorSpace.YCbCr; // assume it's YCbCr
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}
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return jfif != null ? JPEGColorSpace.YCbCr : JPEGColorSpace.RGB;
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}
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case 4:
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if (startOfFrame.components[0].id == 1 && startOfFrame.components[1].id == 2 && startOfFrame.components[2].id == 3 && startOfFrame.components[3].id == 4) {
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// NOTE: Due to a bug in JPEGMetadata, standard format will report RGBA for non-subsampled, non-JFIF files
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return JPEGColorSpace.YCbCrA;
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}
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else if (startOfFrame.components[0].id == 'R' && startOfFrame.components[1].id == 'G' && startOfFrame.components[2].id == 'B' && startOfFrame.components[3].id == 'A') {
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return JPEGColorSpace.RGBA;
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}
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else if (startOfFrame.components[0].id == 'Y' && startOfFrame.components[1].id == 'C' && startOfFrame.components[2].id == 'c' && startOfFrame.components[3].id == 'A') {
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return JPEGColorSpace.PhotoYCCA;
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}
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else if (startOfFrame.components[0].id == 'C' && startOfFrame.components[1].id == 'M' && startOfFrame.components[2].id == 'Y' && startOfFrame.components[3].id == 'K') {
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return JPEGColorSpace.CMYK;
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}
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else if (startOfFrame.components[0].id == 'Y' && startOfFrame.components[1].id == 'C' && startOfFrame.components[2].id == 'c' && startOfFrame.components[3].id == 'K') {
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return JPEGColorSpace.YCCK;
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}
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else {
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// TODO: JPEGMetadata (standard format) will report YCbCrA for 4 channel subsampled... :-/
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// If subsampled, YCCK else CMYK
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for (Frame.Component component : startOfFrame.components) {
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if (component.hSub != 1 || component.vSub != 1) {
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return JPEGColorSpace.YCCK;
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}
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}
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// Saw no special markers, try to guess from the component IDs
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int cid0 = startOfFrame.components[0].id;
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int cid1 = startOfFrame.components[1].id;
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int cid2 = startOfFrame.components[2].id;
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return JPEGColorSpace.CMYK;
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if (cid0 == 1 && cid1 == 2 && cid2 == 3) {
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return JPEGColorSpace.YCbCr; // assume JFIF w/out marker
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}
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else if (cid0 == 'R' && cid1 == 'G' && cid2 == 'B') {
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return JPEGColorSpace.RGB; // ASCII 'R', 'G', 'B'
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}
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else if (cid0 == 'Y' && cid1 == 'C' && cid2 == 'c') {
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return JPEGColorSpace.PhotoYCC; // Java special case: YCc
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}
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else {
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// TODO: Warning!
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return JPEGColorSpace.YCbCr; // assume it's YCbCr
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}
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}
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case 4:
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if (adobeDCT != null) {
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switch (adobeDCT.transform) {
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case AdobeDCT.Unknown:
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return JPEGColorSpace.CMYK;
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case AdobeDCT.YCCK:
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return JPEGColorSpace.YCCK;
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default:
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// TODO: Warning!
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return JPEGColorSpace.YCCK; // assume it's YCCK
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}
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}
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else {
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// Saw no special markers, try to guess from the component IDs
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int cid0 = startOfFrame.components[0].id;
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int cid1 = startOfFrame.components[1].id;
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int cid2 = startOfFrame.components[2].id;
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int cid3 = startOfFrame.components[3].id;
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if (cid0 == 1 && cid1 == 2 && cid2 == 3 && cid3 == 4) {
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return JPEGColorSpace.YCbCrA; // Java special case: YCbCrA
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}
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else if (cid0 == 'R' && cid1 == 'G' && cid2 == 'B' && cid3 == 'A') {
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return JPEGColorSpace.RGBA; // Java special case: RGBA
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}
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else if (cid0 == 'Y' && cid1 == 'C' && cid2 == 'c' && cid3 == 'A') {
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return JPEGColorSpace.PhotoYCCA; // Java special case: YCcA
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}
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else {
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// TODO: Warning!
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// No special markers, assume straight CMYK.
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return JPEGColorSpace.CMYK;
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}
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}
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default:
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throw new IIOException("Cannot determine source color space");
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}
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