# Changeset 1975

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Timestamp:
11/16/07 02:34:32 (6 years ago)
Message:
• Finished gamma correction section.
Location:
www/study
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1 edited

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• ## www/study/part4.html

 r1972

The following figure shows the gamma curve for the naïve three-colour grayscale gradient we saw above (red) compared to the two-colour gradient (blue). Two major observations can be made: the new curve is far closer to a perfect, linear gradient, and there is a singularity in the middle of the curve, meaning a break in the gradient’s smoothness.

grayscale gradient we saw above (red curve) compared to the two-colour gradient (blue curve). Two major observations can be made: the new curve is far closer to a perfect, linear gradient, but there is a singularity in the middle of the curve, meaning a break in the gradient’s smoothness.

is fixed.

• Don’t place the gray value at the middle of the gradient, for instance putting it around 25% itensity will again match the previous two-colour a value of around 25% intensity will again match the previous two-colour gradients.
• Gamma-correct input pixels before assigning them an output value. This ensures that the resulting gradient is perfectly linear. value. This ensures that the resulting gradient is perfectly linear and has no singularity.
• 4.2. Gamma correction

These are the results of gamma-correcting input pixels before doing

Gamma correction consists in converting pixel values into intensity values before performing operations on them, then reconverting them to pixel values before displaying them. The exact same algorithms can be used, they just operate on slightly different data.

Here are the results of gamma-correcting input pixels before doing any computation on them, then using Floyd-Steinberg error diffusion:

Two-colour dithering is not visually satisfying: dark areas lack much detail because the gamma curve is very flat at low intensities. However, the result itself is far more accurate that previously. The problem, while still visible, is even less important with three-colour dithering: the image on the right is superior to what The Gimp or Adobe Photoshop are able to come up with.

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