Alternatively, does it make sense to convert a GIF that you want to decrease
in size to a JPEG, lower its quality and then convert it back to a GIF ? Am
I missing something here ??
Peter Stamboulis
181/2A-15
(301)240-4171
> ----------
> From: Lincoln Perry[SMTP:[EMAIL PROTECTED]]
> Reply To: Lincoln Perry
> Sent: Wednesday, January 05, 2000 11:55 AM
> To: [EMAIL PROTECTED]
> Subject: Re: [JAVA2D] ConvolveOp to reduce image size
>
> >Date: Tue, 4 Jan 2000 18:09:05 -0800
> >From: Austin Chinn <[EMAIL PROTECTED]>
> >Subject: [JAVA2D] ConvolveOp to reduce image size
> >To: [EMAIL PROTECTED]
> >
> >I am creating an image processing program which loads in an image and
> writes
> out different quality versions of the same image. The ultimate goal is to
> reduce the image file size at the expense of some quality. Does anyone
> know how
> to use the ConvolveOp and Kernel to accomplish this? More specifically,
> what is
> the best Kernel config? I would use the codec JPEGEncoder.setQuality(),
> but I
> am also writing out GIFs and my GIFEncoder does not allow me to modify the
> quality. Any ideas/suggestions would be greatly appreciated.
> >
>
> Hi Austin:
>
> GIF is a lossless format, so you can't vary quality in the way you
> can with a lossy format like Jpeg. However, if your GIFEncoder
> supports it, you might be able to reduce the file size by changing
> the color quantization to use a smaller pallette, say a 32 color palette
> instead of a 256 color palette.
>
> I'm not sure that blurring the image will have too big an effect on
> GIF file size. It would have to increase run-lengths significantly
> to help much. But if you want to try it, start with a small kernel,
> like 3x3. Its easiest to think about the values in one dimension
> and then extend it to two dimensions.
>
> You might start with:
>
> float[] kdata1D = {0.1F, 0.8F, 0.1F};
>
> float[] kdata2D = new float[3*3];
>
> for (int y=0; y<3; y++) {
> for (int x=0; x<3; x++) {
> kdata2D[y*3+x] = kdata1D[x] * kdata1D[y];
> }
> }
>
> Kernel kernel = new Kernel(3, 3, kdata2D);
>
> You can vary the elements of kdata until you get the desired blurring
> effect. You lower the central value to get more smoothing. The sum
> of the values in the 1D kernel must be 1.0 and the two outer elements
> should be equal.
>
> [Shameless Plug]
> BTW, you might also want to check out the Java Advanced Imaging API at
> http://java.sun.com/products/java-media/jai
>
> This has a PNG encoder, which might be useful to you.
>
> Regards,
> Link Perry
> JAI Team
>
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