in src/main/java/org/apache/xmlgraphics/image/loader/impl/PreloaderJPEG.java [72:249]
private ImageSize determineSize(ImageInputStream in, ImageContext context)
throws IOException, ImageException {
in.mark();
try {
ImageSize size = new ImageSize();
JPEGFile jpeg = new JPEGFile(in);
while (true) {
int segID = jpeg.readMarkerSegment();
//System.out.println("Segment: " + Integer.toHexString(segID));
switch (segID) {
case SOI:
case NULL:
break;
case APP0:
int reclen = jpeg.readSegmentLength();
in.skipBytes(7);
int densityUnits = in.read();
int xdensity = in.readUnsignedShort();
int ydensity = in.readUnsignedShort();
if (size.getDpiHorizontal() == 0) {
if (densityUnits == 2) {
//dots per centimeter
size.setResolution(
xdensity * UnitConv.IN2CM,
ydensity * UnitConv.IN2CM);
} else if (densityUnits == 1) {
//dots per inch
size.setResolution(xdensity, ydensity);
} else {
//resolution not specified
size.setResolution(context.getSourceResolution());
}
}
if (size.getWidthPx() != 0) {
size.calcSizeFromPixels();
return size;
}
in.skipBytes(reclen - 14);
break;
case APP1:
// see http://www.media.mit.edu/pia/Research/deepview/exif.html
reclen = jpeg.readSegmentLength();
int bytesToEnd = reclen - 2;
// read Exif Header: 0x.45.78.69.66.00.00
int exif = in.readInt(); // 0x.45.78.69.66
in.readUnsignedShort(); // 0x.00.00
// in.skipBytes(6);
bytesToEnd -= 6;
if (exif != EXIF) {
// there may be multiple APP1 segments but we want the Exif one
in.skipBytes(bytesToEnd);
break;
}
// start TIFF data
int currentTIFFOffset = 0;
// byte align: 0x.49.49 (19789) means Intel, 0x.4D.4D means Motorola
int align = in.readUnsignedShort();
bytesToEnd -= 2;
currentTIFFOffset += 2;
ByteOrder originalByteOrder = in.getByteOrder();
// Intel = little, Motorola = big
in.setByteOrder(align == MM ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN);
in.skipBytes(2); // 0x.2A.00 (Intel) or 0x.00.2A (Motorola)
bytesToEnd -= 2;
currentTIFFOffset += 2;
int firstIFDOffset = in.readInt();
bytesToEnd -= 4;
currentTIFFOffset += 4;
in.skipBytes(firstIFDOffset - 8);
bytesToEnd -= firstIFDOffset - 8;
currentTIFFOffset += firstIFDOffset - 8;
int directoryEntries = in.readUnsignedShort();
bytesToEnd -= 2;
currentTIFFOffset += 2;
int resolutionOffset = 0;
int resolutionFormat = 0;
int resolutionUnits = 0;
int resolution = 0;
boolean foundResolution = false;
for (int j = 0; j < directoryEntries; j++) {
int tag = in.readUnsignedShort();
if ((tag == X_RESOLUTION || tag == Y_RESOLUTION) && !foundResolution) {
// 0x011A (XResolution), 0x011B (YResolution)
int format = in.readUnsignedShort();
int components = in.readInt();
int dataByteLength = components * BYTES_PER_COMPONENT[format];
int value = in.readInt();
if (dataByteLength > 4) {
// value is offset to data value
resolutionOffset = value;
} else {
// value is data value
resolution = value;
}
resolutionFormat = format;
foundResolution = true;
} else if (tag == RESOLUTION_UNIT) {
// 0x0128 (ResolutionUnit)
int format = in.readUnsignedShort();
int components = in.readInt();
int dataByteLength = components * BYTES_PER_COMPONENT[format];
if (dataByteLength < 5 && format == 3) {
int value = in.readUnsignedShort();
in.skipBytes(2);
resolutionUnits = value;
} else {
in.skipBytes(4);
}
} else {
in.skipBytes(10);
}
bytesToEnd -= 12;
currentTIFFOffset += 12;
}
in.readInt(); // not needed, but has thumbnail info
bytesToEnd -= 4;
currentTIFFOffset += 4;
if (resolutionOffset != 0) {
in.skipBytes(resolutionOffset - currentTIFFOffset);
bytesToEnd -= resolutionOffset - currentTIFFOffset;
if (resolutionFormat == 5 || resolutionFormat == 10) {
int numerator = in.readInt();
int denominator = in.readInt();
resolution = numerator / denominator;
bytesToEnd -= 8;
}
}
in.skipBytes(bytesToEnd);
in.setByteOrder(originalByteOrder);
if (resolutionUnits == 3) {
// dots per centimeter
size.setResolution(resolution * UnitConv.IN2CM, resolution * UnitConv.IN2CM);
} else if (resolutionUnits == 2) {
// dots per inch
size.setResolution(resolution, resolution);
} else {
// resolution not specified; set default if not set yet
if (size.getDpiHorizontal() == 0) {
size.setResolution(context.getSourceResolution());
}
}
if (size.getWidthPx() != 0) {
size.calcSizeFromPixels();
return size;
}
break;
case SOF0:
case SOF1:
case SOF2: // SOF2 and SOFA are only supported by PDF 1.3
case SOFA:
reclen = jpeg.readSegmentLength();
in.skipBytes(1);
int height = in.readUnsignedShort();
int width = in.readUnsignedShort();
size.setSizeInPixels(width, height);
if (size.getDpiHorizontal() != 0) {
size.calcSizeFromPixels();
return size;
}
in.skipBytes(reclen - 7);
break;
case SOS:
case EOI:
// Break as early as possible (we don't want to read the whole file here)
if (size.getDpiHorizontal() == 0) {
size.setResolution(context.getSourceResolution());
size.calcSizeFromPixels();
}
return size;
default:
jpeg.skipCurrentMarkerSegment();
}
}
} finally {
in.reset();
}
}