Background color bug with indexed colors

andi.k · Post by **andi.k** » Tue Jan 06, 2009 12:42 pm

I have several versions of PhotoImpact (7, XL and 12) and all of them suffer from a bug when exporting to GIF / PNG with indexed colors.

I run into this when scanning text documents, say DIN A4 letters at 300dpi. Before exporting to PNG or GIF, I use the Gradient tool to maximize contrast.

The image is 8bit RGB at this point and contains only black or colored text on white background.

Now, I try to export to GIF or PNG with 8..64 indexed colors via Image optimizer, but PI occasionally changes the background from white to light pink / light blue or some other bright color and PI 12 sometimes even makes the black text or the white background transparent.

Now, I find myself fiddling with the palette - adding a (255,255,255)-white helps returning the background to white. But the transparent text can not be fixed - there is no mask defined for the image. Setting a mask color and removing it doesn't help.

PI even crashed after I played with the Image optimizer options.

To reproduce this issue, just create a DIN A4 300dpi RGB image (2480x3508 pixels) with white background and use the text tool to enter some black text.

Now, use image optimizer to generate an indexed PNG image with 8 colors. The white background will turn to gray (PI XL) or get transparent (PI 12)!!!

This also happens when converting the image to indexed colors with optimized palette.

I tried this with GIMP and other imaging tools - no problem here!

Has anyone run into this before?

Any workarounds / bugfixes available?

Post by **Ron P.** » Tue Jan 06, 2009 1:22 pm

Welcome to the forums,

I don't find the problem. However on the Mask Options tab, I selected Matte, and used white. The other settings I used were:

Colors: 8
Weight: Even
Palette: Optimized
Soft: None
File Type: Indexed
Filter: None
Dither & Interlaced left unchecked

The page remained white (255,255,255), and the text was black and crisp..

andi.k · Post by **andi.k** » Tue Jan 06, 2009 1:35 pm

Thanks for the hint with "Matte" - seems to work around the transparency issue.

But: How big was your image?

I tried it with 640x480 pixels - no prob, but with 2480x3508 white still turns to gray.

Post by **Ron P.** » Tue Jan 06, 2009 1:53 pm

The same dimensions that you specified...

andi.k · Post by **andi.k** » Tue Jan 06, 2009 2:05 pm

Probably, your text was not anti-aliased...

When I disable anti-aliasing for the text tool such that the text is only plain black with no gray tones, I can reduce to 8 colors without probs for the image contains only 2 colors in total

But with anti-aliasing enabled, I definitely run into trouble!

Anyone else?

andi.k · Post by **andi.k** » Mon Jan 12, 2009 7:22 pm

Could anyone please verify this with anti-aliasing enabled?