11/6/2023 0 Comments Gimp replace colorNow create a New Layer (have Foreground set to Red when you do this). There should now be a nice green and alpha image with no trace of the blue left. Click OK after the color indicator on the Color To Alpha plug-in is changed to blue. If using Gimp for Windows, you’ll have to right-click on the destination button and select the Foreground - drag n’ drop doesn’t work. Click, hold, and drag from the color portion of this window to the color portion of the Color To Alpha plug-in. When you used the color picker to select the background, a window with the color popped up. Next use the Color Picker Tool to select the background color. If its not there, upgrade your gimp to 1.2.x. If its grayed-out, it means that you have an indexed image. Its menu location is Filters -> Colors -> Color To Alpha, where means to right click on the image. The first step is to activate the color to alpha plug-in. Instead, may I suggest the rest of the tutorial? Step 1 ¶ I reimplemented this algorithm using PIL for an open source python photo processor phatch.You can find the full implementation here.This a pure PIL implementation and it doesnt have other dependences. You can go too far, and blend it back to something close, but this is time consuming. The best way to do it is to use the 'color to alpha' algorithm used in Gimp to replace a color. Anything short of the rightmost image has some blue in the pixel, which will stick out. You can spend hours trying to find something that will work perfectly, but you won’t. You can try getting rid of all the ugly pixels, but then you’ll end up with something jagged like on the right. The middle one is close, but there are some ugly visible pixels still. This looks somewhat neat, but not what we’re going for. The left one has a blue border around it. When these are filled, we are left with flat black and slightly blueish-green pixels between them, or no transition to black at all.Ĭompare each with the target image below. You’ll note that each of the three zoomed in selections above have varying amounts of the green-blue mix selected. However, when removing an anti-aliased object from its background is not a good idea, as shown above. The common approach to doing many things in GIMP is to first get a good selection. This tutorial doesn’t address the complexities of handling real-world photos in this manner, but does briefly discuss it at the end. To illustrate this, this tutorial will use the above images as source and destination. The aim is to show the advantages of using the color to alpha plug-in over selection-based techniques. This tutorial shows you how you can efficiently replace the background of an image with another in GIMP, through the use of the color to alpha plug-in. (You can also work with the “threshold” to see if this makes the selection/clearing process better, without bleeding any color out of the main object in your image.Text and images Copyright (C) 2002 Seth Burgess and may not be used without permission of the author. This implements the "color select" tool, and you should see some moving highlights around the borders of the color you selected, indicating that every pixel that is of that exact color is now selected.Īfter doing this I still had to do some erasing work in the gray background area, but this technique deleted probably 90-95% of the gray color properly, without pulling any color out of the black phone, which is very important. Add transparency to the image (Click Layer > Transparency > Add Alpha Channel.).(Experiment with the Radius setting, but start with the default value.) In the Tool Options, make the threshold zero. The Color to Alpha command makes transparent all pixels of the active layer that have a selected color.What I did to implement the Stack Exchange instructions was this:
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