On my badly broken Linux desktop,
the Gimp is missing its file-saving plug-ins, so it cannot save
files except in a format I cannot use. XPaint does not
exist, for some reason. The venerable bitmap
program does work, but can only produce
X11 bitmap files (which are black and white only). How then to produce colour icons for my
Picky Picky Game mock-ups?
The answer is, of course, to use Jef Poskanzer’s PBMPlus
Toolkit (as extended over the years by other people to make
NetPBM).
I used this in the
distant past to get around the lack of graphics editors on
Unix in the olden days (we are talking circa 1992, here).
Using bitmap, you make masks for the colours you want,
and combine them using pnmarith.
There was a slight hiccup when I discovered that
pgmtoppm seems to go strange when presented with a
PBM: it generates a depth-1
pixmap, therefore losing the very colours you have just used it
to add. No doubt my decrepit compuer has out-of-date PBMPlus
software, just like everything else...
Anyway, the PBMPlus method for colour graphics is as follows. For each colour (including the white background), you create a bitmap that is the mask for that colour:
The first one is the white mask. The second is white where
I want the picture to be red, and black otherwise. If
there were several colours there would be several of these. In
bitmap producing these masks is relatively
easy—start with the white mask, press Invert, and then
Flood Fill the parts you don’t want.
Convert these to PBM files using xbmtopbm.
Now we start creating the image, one colour at a time. The
first layer, white, is easy: just copy
warning-white.pbm to warning.ppm. For
other colours, you use ppmmake to create a block of
the colour, pnmarith -m to mask out the area you
want, and pnmarith -a to combine this with the main
image:
mv warning.ppm tmp.ppm && ppmmake '#990000' 32 32 |
pnmarith -m - warning-red.pbm |
pnmarith -a - tmp.ppm > warning.ppm
The result is a picture with several colours in it, created using only a bitmap editor:
All in all this is a lot more bother than using a proper WYSIWYG graphics editor. (You also cannot sensibly create images with a large number of colours, since each colour needs its own mask.) When Jeremy’s not using her NT box I might borrow that to produce nicer graphics.