Convert or create PNG images in palette mode in Java

[babz]

AoA ..

does any one know how to create PNG images in Palette mode in java??

PNGQUANT is a software wriiten in C which does the conversion. But i
need java code for that..

Any ideas???

Thanks

Babz

 

[Thomas Fritsch]

AoA ..

does any one know how to create PNG images in Palette mode in java??

PNGQUANT is a software wriiten in C which does the conversion. But i
need java code for that..

Any ideas???

Thanks

Babz

It is rather straight-forward in java. Create a BufferedImage with an
IndexColorModel, and write it to a PNG file using javax.imageio.
The example below writes a simple PNG image (100x100 pixel, red square
on transparent background):

import java.io.*;
import java.awt.*;
import java.awt.image.*;
import javax.imageio.*;

public class Test {
public static void main(String args[]) throws IOException {
int cmap[] = {
0x00000000, /*transparent*/
0xFF000000, /*black*/
0xFFFF0000, /*red*/
0xFFFFFF00, /*yellow*/
0xFF00FF00, /*green*/
//......
};
IndexColorModel colorModel = new IndexColorModel(8,
cmap.length, cmap, 0, true, -1, DataBuffer.TYPE_BYTE);
BufferedImage image = new BufferedImage(100, 100,
BufferedImage.TYPE_BYTE_INDEXED, colorModel);
Graphics2D g = image.createGraphics();
g.setBackground(new Color(0,0,0,0)); /*transparent*/
g.clearRect(0 , 0, image.getWidth(), image.getHeight());
g.setColor(Color.red);
g.draw(new Rectangle(10, 10, 40, 40));
ImageIO.write(image, "PNG", new File("example.png"));
}
}

 

[Roedy Green]

does any one know how to create PNG images in Palette mode in java??

PNGQUANT is a software wriiten in C which does the conversion. But i
need java code for that..

look at the source code for Masker that creates a transparent PNG
image out of thin air. See http://mindprod.com/products1.html#MASKER

 

[babz]

how do you use masker?? any documentation available???

 

[Joan]

how do you use masker?? any documentation available???

it is pretty self explanatory, try it

 

[Roedy Green]

how do you use masker?? any documentation available???

see http://mindprod.com/applets/masker.html

If you want to know how it works, look at the source code
http://mindprod.com/products1.html#MASKER

 

[Roedy Green]

it is pretty self explanatory, try it

When I am feeling more compos mentis I will look into writing a
palette style PNG to keep MS happy.

 

[babz]

it does not serve the purpose. An image converted by pngquant renders
fine in IE but the masked image does not show up properly.

 

[babz]

Thanks Thomas,

The code gives me transparent results but there some prob with the
BLACK color. If a draw a black line, it renders it as transparent. but
for other colors like red, green, etc.. it works fine..

Do u know the reason??

Thanks,

Babz

 

[Thomas Fritsch]

The code gives me transparent results but there some prob with the
BLACK color. If a draw a black line, it renders it as transparent. but
for other colors like red, green, etc.. it works fine..

Do u know the reason??

Your description sounds very much like the known Sun bug
"opaque colors become transparent with IndexColorModel"
<http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4974546>

But: I modified my posted example (replaced "Color.red" by
"Color.black") and rerun it (with Java 1.4.2_05). The generated PNG file
looks OK for me (displaying black on transparent, in Mozilla and IE).

I don't know what is different between mine and yours. I suggest you
post your code fragment here.

 

[Roedy Green]

The code gives me transparent results but there some prob with the
BLACK color. If a draw a black line, it renders it as transparent. but
for other colors like red, green, etc.. it works fine..

Do u know the reason??

lets say you had a pane of clear glass, and you had some transparent
fireflies sitting on the glass flashing their tails.

You could see through the glass but the fireflies would ADD to the
light coming through the glass.

Imagine a sick firefly sitting on the glass not flashing his tail. He
adds nothing to the light coming through the glass. He would just be
transparent as if he were not even there.

The sick firefly is like BLACK on a transparent background.
For black you want the colour to be opaque to be visible.

Black is like lime green used in TV as the transparent colour for
matte work.

P.S. one TV sketch that tickled my funnybone involved a TV weatherman
who wore a lime green suit, and of course became semi-invisible when
they did the map overlays.