Legacy ImageMagick Discussions Archive

Would there be a way to change the gradient color of a part of the image dynamically based on the color of the border pixel? I.e the aura is red when coming out a red book and blue when coming out a blue book? You can do that sort of using distort depolar/polar combination (cartesian to polar and p...

Right. I was brain dead about this. Most of the resampling functions are damped oscillations in approximation of a sinc function. So they have negative lobes.

Thanks. I do understand about HDRI and -clamp. However, I admit I forgot to check that. But I did not realize that -resize would possibly create out of bounds values. Thanks for the explanation.

You need to change the background color under the transparency to your green color. Also you reduce the -evaluate multiply or remove it, since I only used that to exaggerate the white background so it would stand out. convert books.png -background green1 -alpha background \ \( -clone 0 -size 388x361...

That works fine. Thanks. Basically resolved.

But can you explain why it depends upon the -resize. If -resize 100%, it does not happen.

The problem with adding an aurora around an image with transparency is that you will have to modify the transparency so that it is not fully transparent and fades. So you need to invert your gradient (so that it fades to black at the edges) and combine the gradient with the old alpha channel. http:/...

What is the point of this discussion. As I mentioned before there has been a rather extensive study of the benefit of doing resizing in linear light by Nicolas Robidoux on this forum. What new information are you adding?

The command still fails for me in IM 7.0.8.62 Q16 HDRI Mac OSX Sierra. I do not have OpenCL configured in. If I -limit thread 1, it still fails, so not OpenMP. Can you test on your Mac? Note the white lines in the IM 7 result that are not there in the IM 6 result. Also see my comment about it happen...

Yes, but can you point to some reference so that we can see what is being done or is this just some idea of yours with no current background or theory?

The polynomial function uses coefficients not control points, I believe. The d values are coefficients of a polynomial, not control points. Sorry, I do not know the MagickWand API and just use the command line. See https://imagemagick.org/Usage/transform/#function_polynomial To emulate a smooth curv...

You will have more flexibility using magick convert syntax rather than magick composite syntax. In IM 7 replace convert with magick and composite with magick composite. But magick by itself is much more flexible than magick composite. You can use parenthesis processing to scale and offset the waterm...

I have not heard of anything like that for resampling. Can you point to some reference?

You cannot edit the color map in the file with ImageMagick.

Perhaps I misunderstand your question. Do you want to change the color map or the pixel color in the image? If the latter, you can change white to some other color.

It would help considerably if you post an example image to some free image hosting service and put the URL here. Also please always provide your exact ImageMagick version and platform, since syntax may vary. Units of inches are not helpful for raster images. Pixels are what are important. There are ...

The command needs to remove the virtual canvas after the deskew with +repage. I also put in a +fuzz to turn off fuzz for the connected components. Try this: magick testscan.png -rotate 90 -set option:color "%[pixel:u.p{10,10}]" -background "%[color]" -deskew 80% +repage \ \( -clo...