This panel contains the histogram of the frame buffer image. To open the histogram, pull the slider from the rightmost side of the image to the left, or double-click on the right slider.
The histogram enables you:
to visualize the color data within the frame buffer
to set the highlight and shadow clamping points for viewing the buffer by using the Shadow and Highlights sliders at the bottom of the histogram
to increase the dynamic range of the buffer you are viewing, so you can better see the data inside by linearly scaling the colors between the clamp ranges
to distinguish more quickly between small bars and zero-height bars: the histogram bars that have zero height have light gray below them
This drop-down list enables you to configure the channels viewed for the selected frame buffer.
RGB mode – ignores the alpha channel if one is present
RGBA mode – weights the color values by the alpha channel; if all the alpha values of the image are 0, then no color information will be visible, so the image will appear white
Red/Green/Blue Color Channels – shows the image information in red/green/blue color
Grayscale – a grayscale conversion of the RGB data that was present in the buffer
Alpha Channel – a grayscale conversion of only the alpha data of the buffer
Selecting ergs and changing highlighting colors lead to the image and histogram changes.
Auto Clamp Button
This button automatically adjusts the Shadow and Highlighted sliders of the current histogram; they will clamp the view of the buffer to the lowest and highest data points in the histogram respectively. Note that a Grayscale version of the image is used for this clamping, so for some data sets the clamping will produce non-obvious results.
Highest/lowest point refers to the rightmost/leftmost histogram data values that contain non-zero data.