Tutorial 2: Bluescreen Matting

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Now we know the basic idea and workflow of recomposition. It's obvious that most time are spended on select the subject and separate it from background(matting itself),and, the simple selection tool can only deal with simple shape. So, let's find out what 'Bluescreen matting' can do:

The bluescreen matting has been introduced in chapter 1 of the help file, we select a photo meet all its requirements as sample of this toturial. This photo can be found in the 'sample' folder of your software.

After open, select 'It's foreground' and click 'Bluescreen matting' button in the popup dialog, then we enter the matting status:

Use the color picker to click the background, then the program will start processing automatically, and output the result. Sometime if the photo is good, we don't need do any thing further. For this sample, we have such problems:

• 1，Unconstant background, dark area in it.
• 2，The jade on model is green too,which will be treated as background.

So there are defects in result to be fixed, in default block view mode, the defects may not obvious.

But we also find, the black cloth is a little semitransparent. Now we switch view mode to 'Show mask' to find out all of them:

How to fix them. First, adujst the algorithm settings page. There are two parameters you can set in it:
Sensitivity:A small amount will try to keep more pixels as foreground, while large amount tend to discard more. In algorithm, it controls the tolerance range of chroma.
Clear Threshold:Set pixel to transparency where its opacity less than threshold. This parameter can clear the background.

We can use a larger threshold to clear the background, set it and click 'Apply':

Now, the background is almost pure black. The left unwanted part in background can be subtracted by using 'Polygon Modify' tool, subtract mode.

Still 'Polygon Modify' tool, set to 'Add' mode to add the jade and cloth into foreground:

Done! check the result, if there are other defects, fix it.

After finished, Click 'Create complex selection' button or 'Selection status-apply and back' in menu:

Click 'Change background' button, and select the new background file. The program will load the file, and come back to composition mode, and active 'Free transform' tool automatically:

The following step you can refer to the last tutorial, about how to use transform tool in composite status. After that, you can even use external Turbo Photo to blur the background like this:

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