If I overprint this image 20 times using processing 98 I get rounding errors in the
result. (using 15% alpha tint value).

// ramp over printing
// example showing the rounding errors as the image is
// over printed twenty times using 15% transparency.

PImage a;

void setup()
{
size(600, 200);
String ramp = "rampandnoiseOriginal.jpg"; // set String to image name
a = loadImage(ramp);
tint(255,15); // set tint value - colour,alpha
}

float lcv = 100; //loop count variable

void draw() // Main loop
{
image(a, 0, 0); // display image a
lcv = lcv - 5; //decrement loop variable
if (lcv < 0) {
noLoop(); }
}

Here is the link to the original jpg:

[URL=http://img355.imageshack.us/my.php?image=rampandnoiseoriginal6ah.jpg]
[IMG]http://img355.imageshack.us/img355/1341/rampandnoiseoriginal6ah.th.jpg
[/IMG][/URL]

Here is a link to the results:

[URL=http://img355.imageshack.us/my.php?
image=rampandnoisecomparison9qf.jpg][IMG]
http://img355.imageshack.us/img355/9849/rampandnoisecomparison9qf.th.jpg
[/IMG][/URL]

As you can see the image results for both MACOSX(10.3.5 using latest java updates)
and WIN(XP SP2) are different especially if you compare the noise area to the right.
I've also pasted in what 20 layers at 15% look like in photoshop so you can see that
there might be a small problem in processing overprinting code.

Many thanks otherwise for a great application.

Cheers

Sam
London

unfortunately this is either a difference between how macosx and windows
java is implemented, or it's just a difference between your displays (i.e.
mac colorsync is doing something different, or your bit depth isn't
identical), so it's not something i can fix.