Convert BufferedImage from DirectColorModel to IndexColorModel

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Philipp - 10 Dec 2006 20:24 GMT

Hello
I want to be able to save to gif using ImageIO. For this I need to
convert my TYPE_INT_RGB BufferedImage to a TYPE_BYTE_INDEXED BufferedImage.

How can this be done using the quantization algorithms discussed in
javax.media.jai.operator.ColorQuantizerDescriptor.

(I don't seem to understand how all these image operations works).

Thanks for your answers Phil

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hiwa - 10 Dec 2006 23:43 GMT

> Hello
> I want to be able to save to gif using ImageIO. For this I need to
[quoted text clipped - 6 lines]
>
> Thanks for your answers Phil

Make an indexed BufferedImage and draw the original RGB BufferedImage
onto it.

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Philipp - 11 Dec 2006 17:24 GMT

>> Hello
>> I want to be able to save to gif using ImageIO. For this I need to
[quoted text clipped - 8 lines]
> Make an indexed BufferedImage and draw the original RGB BufferedImage
> onto it.

Hello and thanks for the answer.
I tried the following which throws an exception. What do you mean by
"draw onto it"?:

[--code--]
BufferedImage bi = sv.getBufferedImage();
BufferedImage indBI = new BufferedImage(bi.getHeight(), bi.getWidth(),
BufferedImage.TYPE_BYTE_INDEXED);

bi.copyData(indBI.getRaster());
return ImageIO.write(indBI, fileType, file);
[--end--]

The copyData line throws the following:

[--stack trace--]
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: [I
    at
sun.awt.image.ByteInterleavedRaster.setDataElements(ByteInterleavedRaster.java:660)
    at java.awt.image.BufferedImage.copyData(BufferedImage.java:1449)
    at io.BitmapRecorder.writeBitmapFile(BitmapRecorder.java:25)
[--end--]

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Thomas Fritsch - 11 Dec 2006 17:56 GMT

Philipp schrieb:

>>> Hello
>>> I want to be able to save to gif using ImageIO. For this I need to
[quoted text clipped - 14 lines]
> I tried the following which throws an exception. What do you mean by
> "draw onto it"?:

I think he means something like this:
BufferedImage rgbImage = ...;
BufferedImage indexedImage = new BufferedImage(...,
BufferedImage.TYPE_BYTE_INDEXED, ...);
Graphics2D g = indexImage.createGraphics();
g.drawImage(rgbImage, ...);

Signature

Thomas

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Philipp - 12 Dec 2006 09:00 GMT

> Philipp schrieb:
>>
[quoted text clipped - 9 lines]
> Graphics2D g = indexImage.createGraphics();
> g.drawImage(rgbImage, ...);

Hello and thank you for the comment which brought me closer to the
solution I look for.
I tried the following (1) which works as it outputs a gif file, but
a) I think to use RescaleOp as a color conversion tool is ugly
b) the colors output are really ugly (especially because my image has
only 256 colors, so it should be indexable exactly). Can I improve this
with the rendering hints?

I tried other ways which do not work:
(2) ColorConvertOp: I dont know the colorspace to use.
(3) ColorQuantizerDescriptor: This is prob the way to go. Don't know why
it doesn't work. Can you point me in the right direction?

Thanks again Phil

--- [code] (OK works, but colors are ugly) ---

BufferedImage rgbImage = sv.getBufferedImage(); // is of TYPE_INT_RGB
BufferedImage indexedImage = new BufferedImage(rgbImage.getWidth(),
rgbImage.getHeight(), BufferedImage.TYPE_BYTE_INDEXED);
Graphics2D g = indexedImage.createGraphics();
RenderingHints hints = new RenderingHints(RenderingHints.KEY_DITHERING,
RenderingHints.VALUE_DITHER_ENABLE);
RescaleOp op = new RescaleOp(1.0f, 0.0f, hints); // do nothing!
g.drawImage(rgbImage,op,1,1);

---- 2 ----

BufferedImage rgbImage = sv.getBufferedImage(); // is of TYPE_INT_RGB
BufferedImage indexedImage = new BufferedImage(rgbImage.getHeight(),
rgbImage.getWidth(), BufferedImage.TYPE_BYTE_INDEXED);
ColorConvertOp op = new ColorConvertOp(null);
indexedImage = op.filter(rgbImage, indexedImage);
ImageIO.write(indexedImage, "gif", file);

This throws:
Exception in thread "AWT-EventQueue-0"
java.lang.IllegalArgumentException: Destination ColorSpace is undefined
    at java.awt.image.ColorConvertOp.ICCBIFilter(ColorConvertOp.java:290)
    at java.awt.image.ColorConvertOp.filter(ColorConvertOp.java:262)
    at io.BitmapRecorder.writeBitmapFile(BitmapRecorder.java:58)

---- 3 ----

BufferedImage rgbImage = sv.getBufferedImage(); // is of TYPE_INT_RGB
PlanarImage indexedImage =
ColorQuantizerDescriptor.create(rgbImage,ColorQuantizerDescriptor.MEDIANCUT,256,32768,null,1,1,null);
ImageIO.write(indexedImage, "gif", file);

This throws:
Exception in thread "AWT-EventQueue-0"
java.lang.IllegalArgumentException: The specified ColorModel is
incompatible with the image SampleModel.
    at javax.media.jai.PlanarImage.setImageLayout(PlanarImage.java:541)
    at javax.media.jai.RenderedOp.createRendering(RenderedOp.java:878)
    at javax.media.jai.RenderedOp.getColorModel(RenderedOp.java:2253)
    at javax.imageio.ImageTypeSpecifier.<init>(ImageTypeSpecifier.java:226)
    at
javax.imageio.ImageTypeSpecifier.createFromRenderedImage(ImageTypeSpecifier.java:1031)
    at javax.imageio.ImageIO.write(ImageIO.java:1439)
    at javax.imageio.ImageIO.write(ImageIO.java:1488)
    at io.BitmapRecorder.writeBitmapFile(BitmapRecorder.java:65)

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Convert BufferedImage from DirectColorModel to IndexColorModel

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