Legacy ImageMagick Discussions Archive

Hello, I have some images like these ones:



I would like to make the figures on the images (which are currently semi-transparent) be totally opaque, and go from the greyish color they are to being totally white (#ffffff). How would I go about this using convert? All of the images also have these different amounts of alpha on the figures, so I can't do a blind one-color-for-another replace.

nihilazo wrote: ↑2018-10-18T09:03:44-07:00I would like to make the figures on the images (which are currently semi-transparent) be totally opaque, and go from the greyish color they are to being totally white (#ffffff). How would I go about this using convert? All of the images also have these different amounts of alpha on the figures, so I can't do a blind one-color-for-another replace.

There are probably a few good ways to do this. My first thought was to threshold the alpha channel, and fill the positive with white. A command like this gets me pretty close to what you described...
You might be able to tweak the threshold percentage so it accommodates the range of alpha in your various images.

Your alpha channel is the same as your base image. You can see that from comparing the results of

convert test.png -alpha off aoff.png



convert test.png -alpha extract alpha.png




My thought was to make the base image pure white and then threshold the alpha channel.




Looking at GeeMack's solution, it appears to be similar but in the reverse order.

I thresholded the alpha channel more, so that the black lines in the image showed as transparency. If you do not want those outlines, then threshold at 0% (as user snibgo suggested below).

As GeeMack says. To change "partially transparent" to "fully opaque", while leaving fully transparent unchanged, use "-threshold 0".

Thank you everyone! This works perfectly.