Flatten

Flatten divides an image by its corresponding “flat” image (flat fielding), which corrects for uneven illumination. Connect the image to input_link and the flat image to flat_link.

Before the division, a dark value is subtracted from each image. Enter the dark values in “darks”: one or two numbers, for the input image and for the flat image.

• Both images must be the same size and have the same number of bands. They can be multiband images.
• Input values below 0.0 are set to 0.0. Flat values of 0.0 or less are set to 1.0.

• If the flat pixel values are unsigned integers, all the flats are read into memory, so that the average value of each flat can be measured.
• If they are floating point, Flatten assumes the flats are already scaled, each divided by its average value. They are then read one scanline at a time, which needs less memory.

The output is floating point.