Graphics Programs Reference
In-Depth Information
10. In Merge2's Properties panel, choose Stencil from the Operation drop-down
menu.
Looking at your comp now, you can see that it works—short of a color difference
between the foreground and background ( FIGURE 4.24 ). Let's use a Grade node
to fix this shift.
Figure 4.24. The car is now correctly located behind the dashboard.
11. Select Read1 and press the G key to insert a Grade node after it.
As you know from Chapter 2 , you are not allowed to color correct premultiplied
images.Itisoftenhardtotellifanimageispremultipliedornot,butinthiscaseit
is. You can also look at the RGB versus the alpha channels and see that the areas
that are black in the alpha are also black in the RGB.
Since you can't color correct premultiplied images you have to unpremult them.
You can do this in one of two ways: using an Unpremult node before the color
correction (in this case, Grade1) and then a Premult node after it, or using the
(Un)premult By Switch in your Color nodes. Let's practice both.
12. Bring Grade1's Offset property up to around 0.4.
You can see that the whole image, except the dashboard area, turned brighter,
even though you are only correcting the car image ( FIGURE 4.25 ). This is due to
the lack of proper premultiplication. Let's do the two-node method first.
Figure 4.25. The whole image turned brighter.
 
 
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