Be careful when converting between gifs and jpegs. Refer to
the jpeg FAQ for an explanation.
http://www.faqs.org/faqs/jpeg-faq/part1/section-9.html
Adam McMahon
University of Miami
Dept. of Mathematics and Computer Science
On Wed, 5 Jan 2000, Stamboulis, Peter wrote:
> 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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> > [EMAIL PROTECTED] and include in the body of the message "help".
> >
>
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