pamflip, pnmcolormap, pnmquant, pnmremap, pnmrotate, ppmquant: add pages (#11800)

* pamflip, pnmcolormap, pnmquant, pnmremap, pnmrotate, ppmquant: add pages

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Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/pamflip.md

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+# pamflip
+
+> Flip or rotate a PAM or PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pamflip.html>.
+
+- Rotate the input image counter-clockwise for a specific degree:
+
+`pamflip -rotate{{90|180|270}} {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Flip left for right:
+
+`pamflip -leftright {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Flip top for bottom:
+
+`pamflip -topbottom {{path/to/input.pam}} > {{path/to/output.pam}}`
+
+- Flip the input image on the main diagonal:
+
+`pamflip -transpose {{path/to/input.pam}} > {{path/to/output.pam}}`

pages/common/pnmcolormap.md

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+# pnmcolormap
+
+> Create quantization color map for a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pnmcolormap.html>.
+
+- Generate an image using only `n_colors` or less colors as close as possible to the input image:
+
+`pnmcolormap {{n_colors}} {{path/to/input.pnm}} > {{path/to/output.ppm}}`
+
+- Use the splitspread strategy for determining the output colors, possibly producing a better result for images with small details:
+
+`pnmcolormap -splitspread {{n_colors}} {{path/to/input.pnm}} > {{path/to/output.ppm}}`
+
+- Sort the resulting colormap, which is useful for comparing colormaps:
+
+`pnmcolormap -sort {{path/to/input.pnm}} > {{path/to/output.ppm}}`

pages/common/pnmquant.md

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+# pnmquant
+
+> Quantize the colors in a PNM image into a smaller set.
+> This command is a combination of `pnmcolormap` and `pnmremap` and accepts the union of their options, except `-mapfile`.
+> More information: <https://netpbm.sourceforge.net/doc/pnmquant.html>.
+
+- Generate an image using only `n_colors` or less colors as close as possible to the input image:
+
+`pnmquant {{n_colors}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`

pages/common/pnmremap.md

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+# pnmremap
+
+> Replace the colors in a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pnmremap.html>.
+
+- Replace the colors in an image with those in the specified color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Use Floyd-Steinberg dithering for representing colors missing in the color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} -floyd {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Use the first color in the palette for representing colors missing in the color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} -firstisdefault {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Use the specified color for representing colors missing in the color palette:
+
+`pnmremap -mapfile {{path/to/palette_file.ppm}} -missingcolor {{color}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`

pages/common/pnmrotate.md

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+# pnmrotate
+
+> Rotate a PNM image.
+> More information: <https://netpbm.sourceforge.net/doc/pnmrotate.html>.
+
+- Rotate a PNM image by some angle (measured in degrees, counter-clockwise):
+
+`pnmrotate {{angle}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Specify the background color exposed by rotating the input image:
+
+`pnmrotate -background {{color}} {{angle}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`
+
+- Disable anti-aliasing, improving performance but decreasing quality:
+
+`pnmrotate -noantialias {{angle}} {{path/to/input.pnm}} > {{path/to/output.pnm}}`

pages/common/ppmquant.md

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+# ppmquant
+
+> This command has been replaced by `pnmquant` and `pnmremap`.
+> More information: <https://netpbm.sourceforge.net/doc/ppmquant.html>.
+
+- View documentation for `pnmquant`:
+
+`tldr pnmquant`
+
+- View documentation for `pnmremap`:
+
+`tldr pnmremap`