2006.09.27 13:31 "[Tiff] Horizontal prediction for 16bit data", by Joris Van Damme

2006.10.06 22:05 "Re: [Tiff] Inverting color space values in a TIFF file", by Toby Thain

On 7-Oct-06, at 2:03 AM, Richard Nolde wrote:

Tiff list:

I'm working a an extension to tiffcrop that will invert the color space of an image.

For Bilevel and Grayscale images, this makes sense. I use it to convert a negative microfilm image to a positive one.

However, is there a meaningful inversion of a palette color or an RGBA image and would this be done by modifying the palette rather than the data that points

into the palette/lookup tables? What sort of algorithm should be applied to the

data in the palettes? Eg for 8 bit grayscale, I just subtract the value from 255

and for bilevel data, I just invert the bits with ones complement operator. Doing

the same for palette images produces viewable but bizarre images.

Why doesn't inverting the entries in the palette work (leaving pixel indices unchanged)?


Instead, should I simply subtract the values in the palette from 255 for 8 bit per color

images? I assume an Alpha Channel value would not be modified.

My version runs successful on images that have a multiple of 8 bits per pixel and

1 bit per pixel, but I doubt that inverted palette color images mean anything to anyone.

Is there any point in allowing such images to be Inverted?

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