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AccuColor – Color Calibration

AccuColor makes color-calibrated (“true color”) images from multispectral images, using a color checker chart with 24 patches: 18 colors and 6 grays.

Modes

Mode Input What it does More
inspect none Outputs the XYZ values of the 24 patches that AccuColor will use XYZ Values
record a 1 × 24 pixel, 3-band XYZ image Stores the XYZ values of your chart for later calibrations XYZ Values
chart a multiband image of the whole chart Measures the patches and computes the calibration matrix Chart
input a multiband image to calibrate Applies the calibration matrix to make a calibrated color image Input
individual a multiband image that includes the whole chart Measures the chart and calibrates the same image in one pass (Hoku 3.1) see below

Typical workflow

  1. Check the chart values with inspect. If your chart has different values, store them with record. The values are saved, so you only need to do this once for each chart.
  2. Image the color checker chart, and run AccuColor in chart mode on that image to compute the calibration matrix.
  3. Run AccuColor in input mode, with that matrix, on every image from the same imaging session.

Individual mode

If an image contains a full view of the color checker chart, individual mode calibrates that image directly. Enter the four “roi” windows for the corners of the chart, as in chart mode. AccuColor measures the chart, computes the calibration matrix and applies it to the same image. To do this, it first stores the whole image in memory.

Requirements

  • Use only visible bands, covering the visible spectrum, with more than 3 bands. Do not include infrared or ultraviolet images.
  • The images must be 8- or 16-bit unsigned integers.
  • The output is an 8-bit color image for display, with Lab (the default) or RGB “photometry”.