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Showing results for tags 'contrast negate'.
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By November 2017, dmstraker was asking for information about Contrast Negate (https://forum.affinity.serif.com/index.php?/topic/49811-your-big-friendly-guide-to-layer-blend-modes/&tab=comments#comment-250891) . As I found nothing about this point in more recent posts, I give my opinion. I think that the luminosities of the two layers are analyzed, but in the sense of lumas, i.e. L'=0.3R'+0.59G'+0.11B' where all quantities are normalized quantities varying in the (0,1) interval. First a selection is built of areas where lumas are both below 0.5 ou both above 0.5. Then, the upper layer is replaced with its negative within the selection. I enclose a macro, simu_Contrast_Negate.afmacro which (hopefully) does this job —to be imported in the Macro panel. Select the upper layer and run it. An Invert adjustment should be created above the upper layer (allowing to recover the selection from the adjustment mask) simu_Contrast_Negate.afmacro
Still trying to figure out Contrast Negate. Would love for some kind and clever person to tell me what the algorithm is. Latest nugget: Duplicate layer. Add Curves to bottom layer. Pull left node all the way up and the right node all the way down. You now have the original image. Indeed, if you take an image and just do the curves inversion on it, the result looks like a Contrast Negate. So is it something to do with inverting the luminance?