How Are Floating Point Images Displayed in NI-Vision?

Updated Jan 10, 2018

Reported In

Software

  • LabVIEW Full

Driver

  • NI-IMAQ

Issue Details

I am trying to display an image which is stored in floating point format. I've set all of the pixel values to 255, so I expect the image to be white. However, when it is displayed, it is just a black image. Why?

Solution

Grayscale images are displayed in most cases with a 256 gray-scale palette. Because the range for a floating point number is infinite, the image is dynamically adjusted to fit in the 256 possible levels.

  • This is done by taking the maximum and the minimum value, setting those to 255 and 0, and then adjusting the remaining values to fit in between.
  • So if the minimum and maximum values are equal, all pixels are forced to the same value: 0. Unlike 16-bit images, there is no way to disable or modify the way this mapping is performed

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