snibgo

There seems to be something weird in that file, sample.tiff. If we copy it with tiffcp: ``` tiffcp sample.tiff sample2.tiff ``` ... and then repeat your experiments on sample2.tiff, the...

Thanks for narrowing the apparent change. A developer may comment.

> Is there a difference between -evaluate-sequence sum and -evaluate-sequence add? As far as I can see (from experiment and reading the code) there is no difference. > Is there...

Yes. That is the general pattern. `-evaluate {operation} value` applies the operation and value to all the images in the current list. For example, `-evaluate add 23%` will add 23%...

The above is from my knowledge, but see also https://usage.imagemagick.org/layers/#evaluate-sequence I agree, the documentation at https://imagemagick.org/script/command-line-options.php#evaluate could be improved.

> If a tiff or psd has several meta channels, how can one specify which one to use as the alpha channel? Is there a mechanism now? If not, perhaps...

IM has a strategy of trying to write small files, so if all the pixels are gray, it doesn't waste space by writing colour channels. I agree it would be...

As far as I can see, from experiment and the IM code, "-define colorspace:auto-grayscale=off" has no effect when writing JPG, or any format other than PSD (and PSB). Perhaps it...

> Not a solution as I then have to adjust the command-line based on each individual file. Do you? Your program can read TGA files that have RGBA channels, so...

You haven't explained why you can't simply use "-type TrueColorAlpha". Sure, paletted input files will be converted non-paletted, but does that matter to you? If your program has problems reading...