Legacy ImageMagick Discussions Archive

It seems that ImageMagick sets the colorspace to sRGB instead of RGB. Not sure if this is a bug. Changing the colorspace to RGB fixes the problem. Should IM assume an xcf image is RGB by default? Is there something in the image format that indicates this or is it always in the same colorspace? (Of ...

I reproduced the behavior on Ubuntu. Debugging shows that the PNG encoder receives image->gamma=1.0 image_colorspace=2 (GRAY) image->intensity=6 (Rec709Luma) The gamma and intensity are not consistent, and the PNG encoder chooses to use the supplied image->gamma and ignore the image->intensity. Can...

Personally, when I write to tiff, I always specify the compression unless I know the input is from a tiff that I have written. I think that's good advice. And when it's good advice to always change the default behavior, that usually means that the "good advice" behavior should *be* the de...

Behaviour confirmed for v6.8.7-0 under Windows7. Likewise when the input is jpeg-in-tiff, the following fails: convert j.tiff -depth 16 j2.tiff If this behaviour is bad, what would we like to happen? Perhaps: when "-depth 16" is encountered, if the default compression is JPEG, change it t...

$ convert rose.jpg -depth 16 -motion-blur 3 rose.tif convert: BitsPerSample 16 not allowed for JPEG. `JPEGSetupEncode' @ error/tiff.c/TIFFErrors/563. It looks like IM wants to use jpeg compression inside the tiff output file because my input file was jpg. It can't apply jpeg compression to 16-bit d...

Is it a bug? "-colorspace gray" makes the image non-linear. If it is followed by "-colorspace sRGB", that will do nothing. I know nothing about PGM. The -intensity rec709luminance means -colorspace gray result will be linear (i.e. luminance), and now flagged by gamma=1 (unfortun...

Yes! I agree with you 100%. But then why doesn't the colorspace of a grayscale image show as "RGB" or "sRGB" in IM? Instead it shows as "gray", from which we can't tell whether its values represent linear (RGB) data or nonlinear (sRGB) data. Yes. I'd like IM to show th...

At Fred's suggestion, the Gray colorspace can continue to behave as it does for script compatibility reasons. Edit: Another reason that Glennrp pointed out for retaining (rather than replacing/redefining) Gray is that Gray also serves as a more generic grayscale colorspace (e.g. I would say whose in...

The difference is that linear RGB is a valid colorspace at least for PNG. But PNG only knows about gray being linear or non-linear by its gamma value. I do not believe the PNG standard supports special gray colorspaces. Also sRGB is not exactly the same as applying gamma=2.2. It has a way of indica...

I still do not understand what good this does. It is only good internally to IM. No other output format will understand these colorspaces. IM can already produce CIE Y linear gray via -grayscale rec709luminance as colorspace gray with gamma=1. Since it is what you want (correct me if I am wrong), w...

It appears to me that the symbols R, G, and B in the list of formulas in the -colorspace entry of command-line-options.html are being used to represent somewhat different things in different places. For example, the XYZ and sRGB formulas are correct only if the symbols R,G,B refer to the linear R709...

Glennrp, what's the next step for your proposal to add two explicit colorspaces in addition to the generic gray? Fred, just to explain my last response further As I said, once the conversions are applied correctly (which involves a different set of coefficients), rec709luminance values should be nu...

If I understand you correctly, you want a new colorspace lineargray or some such thing. But this would only be understood internally by IM. I do not believe any image format would know what to do with that (lineargray named) colorspace. Glennrp can correct me. Almost none of our internal colorspace...

I prefer GrayLog and GrayLinear (as well as Gray which would mean gamma is unspecified). I'm fine with GrayLinear (I think it''s clear enough, even if it could be said to beg the question, linear in what or linearly-related to what?, the most specific answers being that it's a linear function of Lu...

Maybe this is going beyond what you're saying, but how can gray be treated the same as colors in general when colors have essential colorspace distinctions like RGB vs sRGB and the Gray colorspace stores no such distinctions (unless we try to convey this via image->gamma for grayscale images only)?...