Mar Posted February 24, 2010 Share Posted February 24, 2010 Hello everyone! My scenario is this: I have a high contrast black-and-white fishnet pattern, this one in fact, and want to remove the white background. As you can see there is some small white specks amidst the black threads which makes the magic wand produce less than desirable results. Now, what I tried was to simply add a new transparent layer beneath the B&W original and setting the original's blend mode to Multiply. In my mind, this would superimpose the black threads over the transparent blackground, alas I was proven wrong. The annoying thing is I can fill this new layer with red and have the threads come through beautifully with no aliasing and no white specks. Indeed, the process seems very simple if only there was some way of preserving the transparency through the process. Am I doing something wrong and is there a solution better than the not-so-magic wand? I've heard there is an [outdated] plugin that does approximately what I'm after but I'd rather keep to "vanilla Paint.net" if possible. Quote Link to comment Share on other sites More sharing options...
Sarkut Posted February 24, 2010 Share Posted February 24, 2010 (edited) Mar, To eliminate the white from the mesh image: Use Grim Color Reaper plugin, set to white. Save As... PNG. Grim Color Reaper HOW TO INSTALL PLUGINS Edited April 6, 2010 by Sarkut Quote Link to comment Share on other sites More sharing options...
Mar Posted February 24, 2010 Author Share Posted February 24, 2010 It performs beautifully, thank you (On the same note, would anyone kindly explain why Multiply didn't act as I had hoped?) Quote Link to comment Share on other sites More sharing options...
Sarkut Posted February 24, 2010 Share Posted February 24, 2010 This is my best guess. It seems that what is being multiplied with Multiply blend mode are the RGB numbers.. The Alpha channel is separate from the calculation. The Color Picker tool shows Alpha as R255, G255, B255 (white), so it multiplies as white. White is 100%, or one. 1 X 1 = 1 White X Alpha = White Quote Link to comment Share on other sites More sharing options...
Mar Posted February 24, 2010 Author Share Posted February 24, 2010 If I fill the background with #000000, Alpha: 0.0, I should expect to get a completely black result as the net is #000 * #000 and the spaces are #FFF * #000. The result is actually the same as the original: a black net with white, non transparent holes. It seems there is either an invisible white bottom layer that gets added at the very end of the process, or that #000000:0.0 somehow translates to #FFFFFF:1.0... Quote Link to comment Share on other sites More sharing options...
Sarkut Posted February 24, 2010 Share Posted February 24, 2010 (edited) Good point. I'm sure someone knows the answer. In the meantime I will regard it as simply being the will of Vishnu. Edited May 5, 2010 by Sarkut Quote Link to comment Share on other sites More sharing options...
Simon Brown Posted February 24, 2010 Share Posted February 24, 2010 It's blending the colour you're filling with the background, not replacing it. To get it to replace, set the blending mode (not blend mode) to overwrite. Quote Link to comment Share on other sites More sharing options...
Sarkut Posted February 24, 2010 Share Posted February 24, 2010 I'm sticking with my Vishnu hypothesis. Quote Link to comment Share on other sites More sharing options...
Mar Posted February 24, 2010 Author Share Posted February 24, 2010 It's blending the colour you're filling with the background, not replacing it. To get it to replace, set the blending mode (not blend mode) to overwrite. I think you misunderstand what I'm trying to do (or maybe I'm the one misunderstanding what you're trying to say ) To elaborate, I'm not tampering with the original layer in any way other than setting it to multiply. Doing this will let the layer below show through in the white areas, but not if the layer below is transparent. Sarkut reasoned this was because the Multiply layer blending mode disregards the alpha channel, thus blending white with white resulting in white. While this holds true for a completely transparent background with a colour value of #FFFFFF, it shouldn't work that way with a completely transparant #000000. Quote Link to comment Share on other sites More sharing options...
Sarkut Posted February 24, 2010 Share Posted February 24, 2010 Okay. I think the way it works is that the degree of Opacity determines the degree that the blend mode is in force at a given pixel coordinate. Where the Opacity is zero on either layer, the multiply blend mode is rendered null. Wherever zero opacity is present on either layer Normal blend mode is in effect. The amount of transparency apparently multiplies also. If each layer is at 50% transparency, when merged in multiply mode they will have 25% transparency. When both start with 80%, they have 64% when merged with multiply blend mode. Quote Link to comment Share on other sites More sharing options...
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