324 CHAPTER 8 COLOR MANIPULATION, CHANNELS, AND (Web server hosting)
324 CHAPTER 8 COLOR MANIPULATION, CHANNELS, AND LAYER MODES Figure 8-28. The color channels How to Use Color Decomposition Remember Decompose, discussed earlier under Working with Grayscale or Black and White ? There, you saw how to use it to convert images to grayscale in several different ways. But it s far more useful than that. What interesting things can you do with color decomposition? Well, for example, you could select that flower in Figure 8-28. If you right-click on the blue channel (in the Channel Dialog) and choose Channel to Selection, the marching ants make it look like you have a pretty good selection of the flower. But that s deceptive. There s a problem: nothing is completely selected. The flower was mostly blue, but not pure blue, so it gets mostly selected. The grass around the flower has some blue, so a little bit of that gets into the selection too. Instead of getting all of the flower and none of the grass, you get a mostly opaque flower and mostly transparent grass. If you paste the selection onto a white background, you ll see something like Figure 8-29. It might make a nice background for stationery, but it s not what you d want most of the time. Decomposing to RGB can give a better result. Figure 8-30 shows the blue layer, which is basically the same as the blue channel. You can see lots of pieces of the background, not just the flower. But since it s in a layer now, you can modify it to be more useful.
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