## FAQ: Why do the colours of the PNG file not match CSS colours?

This is probably caused by some embedded colour space information; see below
for how to remove this.

## HOWTO: Remove color space information from PNG files (pngcrush)

(You might want to do this to ensure that PNG colours match CSS colours.)

    $ pngcrush -rem gAMA -rem cHRM -rem iCCP -rem sRGB infile.png outfile.png

See

    http://hsivonen.iki.fi/png-gamma/

(Or, convert to GIF...)

## HOWTO: (Losslessly) compress PNGs (pngcrush)

    $ pngcrush image.png -rem alla -reduce result.png
    
See

    http://developer.yahoo.net/blog/archives/2008/03/yahoos_latest_p.html

## TIP: ImageMagick tips

See

    http://www.cit.gu.edu.au/~anthony/graphics/imagick/

## HOWTO: Convert string to image using TrueType font (ImageMagick)

Text on command line:

    $ convert -background white -fill black -font ~/Library/Fonts/P22UNDER.TTF \
      -transparent white -pointsize 72 label:"Holloway Rd" holloway.gif

Text in file:

    $ convert -background white -fill black -font ~/Library/Fonts/P22UNDER.TTF \
      -transparent white -pointsize 72 label:@holloway.txt holloway.gif

(This does do anti-aliasing, but I couldn't get a separate "matte"
colour working...)

HOWTO: Crop an image (ImageMagick)

    $ convert -mattecolor black src.jpg -crop 70x70+0+0 -size 70x70 +repage dst.jpg

ImageMagick 6+ use the "new" command-line parameter handling--the hard
bit is to make sure the different bits are specified in the right order!

## HOWTO: Mark a particular color as "transparent"

(Known as "Color to Alpha" in gimp.)

Use imagemagick:

    $ convert -transparent white foo.png bar.png

(I don't know how to do this with Pixelmator.)

## HOWTO: Strip comments from JPEGs (jpegtran)

    $ jpegtran -copy none -optimize -perfect src.jpg dst.jpg
    
See

    http://developer.yahoo.net/blog/archives/2008/03/yahoos_latest_p.html

## HOWTO: Create contact sheets from video

i.e. extract frames/thumbnails from video.

Use QuickTime export function with the "Movie to Image Sequence" option.
Enter a very small number of frames per second, like 0.01.  Then, invoke
ImageMagick's `montage` with options like:

    $ montage *.jpg -tile 3x -geometry 300x+0+0 montage.jpg

If you get some errors like

    sh: gs: command not found
    montage: unable to read font (null)' @ annotate.c/RenderFreetype/1316.

just ignore them--chances are `montage.jpg` has successfully been created.

This will create a contact sheet of all the `*.jpg` images in the current
directory, with three columns (and however many rows are required), resizing
the images to exactly 300 pixels wide (and however many pixels high required
to maintain the correct aspect ratio) with no border.

For more information on the various options, see
<http://www.imagemagick.org/Usage/montage/>.

## HOWTO: Create contact sheets from a directory of thumbnails from
different images

BROKEN!  Doesn't work for filenames with spaces in the name!

    $ for f in ls | perl -pe 's/\d+.png$//' | uniq ; do montage $f* -tile 3x -geometry 300x+0+0 $f.jpg ; done