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Is there a way to get the component images corresponding Y, Cb, Cr in photoshop. I just need to combine them in layers to see how they form the original image.

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2 Answers 2

I don't believe so -- about the closest Photoshop supports would be CIE L*a*b* (aka CIELAB) color space. From a mathematical viewpoint, the numbers you get with them don't match up at all1, but to simply look at it and get an idea of how those channels combine into a picture, it's probably close enough.

To get to this, you'd start by going to image | mode and selecting "Lab Color". Then to view the individual channels, go to Window | Channels, and you can click the "eyeball" next to each channel to make that channel visible or not.

1In CIELAB, the color space is treated as a cylinder. The three numbers define a coordinate as the distance along the cylinder from bottom to top, an angle of rotation around the cylinder, and the distance out from the center of the cylinder.

In YCrCb, the color space is treated as a cube. The Y coordinate defines the distance long the cube from top to bottom (almost identical to the L coordinate in CIELAB). Cr and Cb, however, define distances along the x and y coordinates of a plane at that height in the cube. This makes the numbers quite a bit different, even though the channels are otherwise roughly similar in nature.

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First thing to show up in Google was a link to a Gimp plugin called "Decompose". You'll probably see an equivalent for Photoshop. They have a corresponding recompose as well.

In general, there are two concepts to keep in mind: Image "Mode" and Layers. The Image "Mode" has to do with whether the layers of your color image are split into RGB, Grayscale (one layer), CMYK, or YCbCr. The first step you need to do is to change your picture's mode if necessary.

After that, go to the Layers control panel and you will see three tabs. You want the "Channels" tab. That will have one channel per component with the slightly different look due to the way the channel is interpreted. For example, you may find you get better results by applying curves to only the Y (luminance) channel.

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That's built-in to Gimp, not a plugin. (It may have been a plugin several versions ago.) –  mattdm Feb 7 '11 at 14:12
    
It's a standard plugin that gets installed with the application. In programming terms, it's techinically a plugin. –  Berin Loritsch Feb 7 '11 at 15:06
    
Why so it is. In modern Gimp, it doesn't show up under filters, which I guess I still have associated with plug-ins in my mind even though I shouldn't. (It's on the Colors menu.) –  mattdm Feb 7 '11 at 19:38

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