Apple Shake 4 - Manual (Page 631)

Chapter 23 Color Correction 631
Value Range
Shake numerically describes color as a range of 0 to 1 (0, 0, 0 is black; 1, 1, 1 is white).
However, you can set a different numeric range—for example, 0, 0, 0 as black, and 255,
255, 255 as white.
Hexadecimal
This button toggles the numeric display to hexadecimal values.
Min/Max Basis
The Min/Max Basis buttons set the channel for calculation of the Minimum and
Maximum swatches. Normally, this parameter is set to L (luminance). To determine the
minimum values in only the red channel, toggle the Min/Max Basis to R (red). For
example, one pure red pixel and one pure green pixel are equivalent pixels based on
luminance. However, based on red, the green pixel has a minimum value of 0, and
therefore the Minimum swatch returns a different value.
Custom Entries
You can insert your own functions to return data using the following code. You provide
a label and the function in a ui.h file. The two default plugs are called exp10 and expf:
gui.pixelAnalyzer.customLabel1 = “exp10”;
gui.pixelAnalyzer.customFunc1 = “(int)(1024*log(l/0.18)/log(10))”;
gui.pixelAnalyzer.customLabel2 = “expf”;
gui.pixelAnalyzer.customFunc2 = “log(l/0.18)/log(10)”;
The PixelAnalyzer Node
The PixelAnalyzer node, located in the Other tab, allows you to examine one or more
areas of an image over a range of frames. The data is then stored as the average,
minimum, and maximum values of each area on a frame-by-frame basis. This data can
then be used by other nodes to perform tasks such as matching colors, or reducing
flickering in a plate. This is done by feeding image data from a PixelAnalyzer node into
expressions within one of Shake’s color-correction nodes.
Using the PixelAnalyzer Node
The workflow used for analyzing color with the PixelAnalyzer node is similar to that of
the Tracker. However, the analyzer does not do any motion tracking itself. It merely
grabs color values at the position of the defined analysis areas.
Note: The analysis areas can be animated, and can also be moved via data from a
Tracker node. Use expressions to assign track data to the areaX and areaY parameters
of the analysis area you want to match to the movement of a tracker.
When using the PixelAnalyzer node, it’s important to make sure that it’s loaded into the
Viewer prior to performing the analysis. Otherwise, the analysis cannot be performed.