PlotScanline
Function This analysis tool examines a line of an image and graphs the intensity of each channel per x position. It is extremely helpful in determining what a color correction function is doing. Although you can attach it to any image to analyze it, you often attach it to a horizontal Ramp to observe a color corrections behavior. By switching the Viewer to view the alpha channel (hit A in the viewer), you can see the behavior of the alpha channel as well.
Here are some examples:
Example 1
A 256x256 8-bit black and white Ramp. Since we have a smooth gradation, with the center at .5, we see a straight line. Moving the center to .75 pushes the center to the right, making the entire image darker. This is reflected in the PlotScanline:
![]() |
![]() |
![]() |
Example 2
Insert color correction nodes and play around with the values. The PlotScanline will indicate exactly what data gets clipped, crunched, compressed or confused:
![]() |
![]() |
Parameters
|
Type
|
Defaults
|
Function
|
width,height |
int
|
width, 512
|
The width and height of the PlotScanline. You probably want to set the width to 256 on an 8-bit image to get 1-to-1 correspondence. |
line |
int
|
0
|
The Y-line of the image to be analyzed. On a horizontal ramp, this doesn't matter, since they are all identical. |
Synopsis
image PlotScanline( image, int width, int height, int line );
Script
image = PlotScanline(image, width, height, line);
Command Line
shake -plotscanline width height line
See Also
Histogram