John Rostron Posted June 5, 2019 Share Posted June 5, 2019 In a discussion of creating a saturation mask, @dmstraker and @smadell referred to an equation involving channels: Saturation=(max(SR,SG,SB)-min(SR,SG,SB))/max(SR,SG,SB) The only way I can see to access these Source Channels is in Apply Image. However Apply Image deals with two images, a Source and a Destination. This calculation deals with just one. The information on Field Equations in Filter > Distort > Equations makes no mention of channels. How would I create a greyscale saturation layer from an RGB layer, which I can then convert to a mask? John Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
R C-R Posted June 5, 2019 Share Posted June 5, 2019 55 minutes ago, John Rostron said: In a discussion of creating a saturation mask, @dmstraker and @smadell referred to an equation involving channels ... Do you have a link to that discussion? Quote All 3 1.10.8, & all 3 V2.4.1 Mac apps; 2020 iMac 27"; 3.8GHz i7, Radeon Pro 5700, 32GB RAM; macOS 10.15.7 Affinity Photo 1.10.8; Affinity Designer 1.108; & all 3 V2 apps for iPad; 6th Generation iPad 32 GB; Apple Pencil; iPadOS 15.7 Link to comment Share on other sites More sharing options...
smadell Posted June 5, 2019 Share Posted June 5, 2019 Hey, John and R C-R... First of all, the link to that series of posts is: https://forum.affinity.serif.com/index.php?/topic/76900-saturation-masks-a-simple-method/ Second, Apply Image really only needs a single image (in fact, a single layer) since there is a button near the top of the dialog box that says "Use Current Layer as Source." Clicking that lets you apply the layer to itself. Here is a screen shot where I swapped the Red and Green channels in a photo (original on the left, swapped channels on the right). The more important point might be that your last question is easier to answer than Dave Straker's math makes it out to be. I have posted a series of macros which will (i) create Saturation masks and Vibrance masks (inverted Saturation masks); (ii) create greyscale visualization layers for those masks; and (iii) allow you to apply the masks to a layer stack. You can access those macros here: https://forum.affinity.serif.com/index.php?/topic/87004-macro-updates-for-v17/ jaanco66 1 Quote Affinity Photo 2, Affinity Publisher 2, Affinity Designer 2 (latest retail versions) - desktop & iPad Culling - FastRawViewer; Raw Developer - Capture One Pro; Asset Management - Photo Supreme Mac Studio with M2 Max (2023}; 64 GB RAM; macOS 13 (Ventura); Mac Studio Display - iPad Air 4th Gen; iPadOS 17 Link to comment Share on other sites More sharing options...
John Rostron Posted June 5, 2019 Author Share Posted June 5, 2019 59 minutes ago, R C-R said: Do you have a link to that discussion? Sorry it was not there originally. I cannot copy/paste the url when using Chrome on my tablet. Anyway, here is the link. John Quote Windows 10, Affinity Photo 1.10.5 Designer 1.10.5 and Publisher 1.10.5 (mainly Photo), now ex-Adobe CC CPU: AMD A6-3670. RAM: 16 GB DDR3 @ 666MHz, Graphics: 2047MB NVIDIA GeForce GT 630 Link to comment Share on other sites More sharing options...
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