adding dither function #33
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Thank you very much for your contribution.
Sorry it took so long for someone to review your PR. This is just a read-only mirror of the upstream Mercurial repository. (But we try to port PR from here to the upstream repository if possible.)
I haven't checked the new function yet. But I left a few comments about the coding style that is used in Octave.
For the time being, I only took a look at the function documentation and had a very quick look at the function bodies (mostly for style).
I didn't bother to leave a comment at each and every line where the style should be adapted. But I tried to describe the coding style at some examples.
scripts/image/dither.m
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| print_usage; | ||
| endif | ||
| if ndims (RGB) == 2 | ||
| RGB = cat (3, RGB, RGB, RGB); % Duplicate grayscale to RGB |
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For end-of line comments, use two spaces and a single # as the comment character.
scripts/image/dither.m
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| endif | ||
| endif | ||
| if ndims (RGB) != 3 || size (RGB, 3) != 3 | ||
| error('dither: RGB must be an m x n x 3 array.'); |
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Use a whitespace between function name and opening parenthesis.
scripts/image/dither.m
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| if ndims (RGB) != 3 || size (RGB, 3) != 3 | ||
| error('dither: RGB must be an m x n x 3 array.'); | ||
| end | ||
| if !ismatrix (map) || size (map, 2) != 3 || min (map(:)) < 0 || max (map(:)) > 1 |
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Use a space after the negation operator (i.e., ! ismatrix (map)).
Use parenthesis around the condition in if statements.
scripts/image/dither.m
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| endif | ||
| Qe = min (Qe, 16); % Cap Qe to avoid excessive precision | ||
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| % Scale RGB and map to [0, 1] |
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Use ## to introduce comments that span the entire line.
| ## @deftypefn {Function File} {@var{X} = } dither (@var{RGB}, @var{map}) | ||
| ## @deftypefnx {Function File} {@var{X} = } dither (@var{RGB}, @var{map}, @var{Qm}, @var{Qe}) | ||
| ## @deftypefnx {Function File} {@var{BW} = } dither (@var{I}) | ||
| ## |
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Please add a one-line description of the function if possible.
scripts/image/dither.m
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| ## @code{@var{X} = dither (@var{RGB},@var{map})} creates an indexed image | ||
| ## approximation, using the color provided in the colormap, and uses dithering | ||
| ## to increase apparent color resolution. Floyd-Steinberg error filter is used: |
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This sentence is pretty long. Consider splitting it into two sentences.
scripts/image/dither.m
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| ## to increase apparent color resolution. Floyd-Steinberg error filter is used: | ||
| ## [ x 7] | ||
| ## [3 5 1] / 16 | ||
| ## It used a raster scan and no weight renormalization at boundaries. |
scripts/image/dither.m
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| ## It used a raster scan and no weight renormalization at boundaries. | ||
| ## The default values are used: @var{Qm}=5, and @var{Qe}=8. | ||
| ## | ||
| ## Inputs: |
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We usually don't use "section headings" like this. Also note, that texinfo will convert this and the following four lines into one single long line.
scripts/image/dither.m
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| ## error calculations in the Floyd-Steinberg error diffusion algorithm. | ||
| ## It controls the precision of the error values that are calculated and | ||
| ## propagated during dithering. If @var{Qe} < @var{Qm}, the error diffusion | ||
| ## process may lose precision, therefore dithering cannot be performed, and the |
2 participants
I've made an implementation of the dither function, compatible with Matlab implementation (https://www.mathworks.com/help/matlab/ref/dither.html). In Matlab it seems not to be a part of Image package, so I guess it would also fit directly into octave core.