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Transform

A basic command-line image processing script for bitmap images written from scratch in C.

Support

  • Supports BMP v3, BMP v4 and BMP v5.
  • Supports 24-bit and 32-bit bitmap images.
  • Does not support color palettes.
  • Does not support compression.

Usage

./transform [options] <input file> <output file>

Options:

  • -i

    Invert colors of image.

    ./transform sampleImages/marbles.bmp invert.bmp -i
    Original Inverted
    Original Inverted

  • -l <factor>

    Apply log gamma transform (natural log) with a multiplication <factor>.

    ./transform sampleImages/lightLarge.bmp log.bmp -l 30
    Original Log Gamma
    Original Log Gamma

  • -e <factor>

    Apply inverse log gamma transform (natural log) with a multiplication <factor>.

    ./transform sampleImages/lightLarge.bmp inverseLog.bmp -e 0.001
    Original Inverse Log Gamma
    Original Inverse Log Gamma

  • -p <gamma>

    Apply power-law gamma transform - RGB intensities are raised to the power (1 / <gamma>).

    ./transform sampleImages/harvard.bmp gamma.bmp -p 2.0
    Original Power-Law Gamma
    Original Power-Law Gamma

    To apply the inverse gamma transform use (1 / original gamma) as <gamma> value.

    ./transform sampleImages/harvard.bmp inverseGamma.bmp -p 0.5
    Original Inverse Power-Law Gamma
    Original Inverse Power-Law Gamma

    Example: To get inverse of <gamma> = 2.0 set <gamma> = 0.5

    ./transform sampleImages/harvard.bmp gamma.bmp -p 2.0 
./transform gamma.bmp retrieve.bmp -p 0.5
    Original Power-Law Gamma Inverse of Power-Law Gamma
    Original Power-Law Gamma Inverse

    Note: We have significant banding or loss of data in the highlights as the original image's hightights were already blown out.

    We can also do this in a single step:

    ./transform sampleImages/lightLarge.bmp retrieveLight.bmp -p 2.0 -p 0.5
    Original Retrieved
    Original Retrieved

  • -g

    Convert image to 8-bit greyscale image.

    Note: Any options provided after this will be discarded.

    ./transform sampleImages/cat.bmp grey.bmp -g
    Original Greyscale
    Original Power-Law Gamma

  • -b

    Bit plane slicing:

    Convert image to greyscale and generate 8 1-bit monochrome images representing each bit plane ranging from MSB (Most Significant Bit) to LSB (Least Significant Bit) - Bit numbering.

    Note: Any options provided after this will be discarded.

    ./transform sampleImages/lightLarge.bmp out.bmp -b
    Original Greyscale
    Original Greyscale
    BitPlane 0 BitPlane 1 BitPlane 2 BitPlane 3
    0 1 2 3
    BitPlane 4 BitPlane 5 BitPlane 6 BitPlane 7
    4 5 6 7

  • -s[=ATTR_LIST]

    Set a range of RGB intensities to specified intensity.

    Attributes: "Ra, Rb, Ri, Ga, Gb, Gi, Ba, Bb, Bi"

    Intensities a to b are set to intensity i.

    ./transform sampleImages/harvard.bmp intensities.out -s150,255,255,50,100,100,200,255,200
    Original Intensities
    Original Intensities

Note:

The order in which the options are provided are the order in which the transforms are applied.