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#1 Posted : Thursday, September 20, 2007 7:22:03 PM(UTC)

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Posts: 2

I am new to Leadtools and I cannot seem to find what the best method for removing a blue background on a photo is. I have been playing with the SubtractBackgroundCommand class in the .NET ImageProcessing assembly. We have Leadtools v15. What I am finding is that this tool is best used for grayscale images and not color photos. Is there a better method for doing this that I am missing. I am attaching a sample photo.

Thanks for any help you can offer.
pshirley attached the following image(s):
michael levi.jpg

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#2 Posted : Friday, September 21, 2007 10:08:28 AM(UTC)


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Posts: 764

What are you wanting to do with the background, what does "removal" entail?  If you simply want to change the color then you can use RasterImage.AddColor[Rgb or Hsv]RangeToRegion method using RasterRegionCombineMode.Set.  If you've tweaked the colorrange correctly then you can run a FillCommand on the image to swap out the color.  If you want to select all of the pixels of the person, you can use the RasterRegionCombineMode.Not.

The only downside to this is if the person has something them (clothes, eyes, makeup) that matches the background and then you'll end up erasing or losing that portion as well.  Also, the shadow that it on the right side of the person will still be there.  Depending on what you're actually doing with the image, this might be acceptable.

If you have problems, please explain your goals in more detail and what problems you're having.
#3 Posted : Friday, September 21, 2007 5:03:11 PM(UTC)

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The approach you specify might work for me. I need to replace the blue background with pure white. The issue is that the image needs to be printed and if the background is anything but pure white then the background is printed. That said I do have the concern about finding the edge of the person. I cannot replace a blue shirt or blue eyes with white. So if you could expand a little on your approach or supply some sample code I would appreciate it.
#4 Posted : Monday, September 24, 2007 7:25:13 AM(UTC)


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Posts: 764

I have created a small C# example that:

1. Shows how to select a color with RasterImage.GetPixelColor
2. Creates a region from a color range with RasterImage.AddColorRgbRangeToRegion
3. Fills the region with the FillCommand class.

This project is very similar to Adobe Photoshop's color range selection tool.

As for the problems such as eyes, shirts, etc. you will either need to make some kind of "safe" area that cannot be selected or you'll have or change your approach completely to some kind of a fill search rather than using AddColorRgbRangeToRegion.  To implement a "safe" area you'll need to play with the different combine modes to find a logic that works for you.
File Attachment(s):
NET - v15 - AddColorRgbRangeToRegion.zip (271kb) downloaded 42 time(s).
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