+# Build the base _icon_ images, by careful cropping of the base
+# images: icons are very small so it's often necessary to zoom in
+# on a smaller portion of the screenshot.
+blackbox-ibase.png : override CROP=352x352 144x144+0+208
+bridges-ibase.png : override CROP=264x264 107x107+157+157
+dominosa-ibase.png : override CROP=304x272 152x152+152+0
+fifteen-ibase.png : override CROP=240x240 120x120+0+120
+flip-ibase.png : override CROP=288x288 145x145+120+72
+guess-ibase.png : override CROP=263x420 178x178+75+17
+inertia-ibase.png : override CROP=321x321 128x128+193+0
+lightup-ibase.png : override CROP=256x256 112x112+144+0
+loopy-ibase.png : override CROP=257x257 113x113+0+0
+mines-ibase.png : override CROP=240x240 110x110+130+130
+net-ibase.png : override CROP=193x193 113x113+0+80
+netslide-ibase.png : override CROP=289x289 144x144+0+0
+pattern-ibase.png : override CROP=384x384 223x223+0+0
+pegs-ibase.png : override CROP=263x263 147x147+116+0
+rect-ibase.png : override CROP=205x205 115x115+90+0
+sixteen-ibase.png : override CROP=288x288 144x144+144+144
+slant-ibase.png : override CROP=321x321 160x160+160+160
+solo-ibase.png : override CROP=321x321 97x97+16+16
+tents-ibase.png : override CROP=320x320 165x165+142+0
+twiddle-ibase.png : override CROP=192x192 102x102+69+21
+untangle-ibase.png : override CROP=320x320 164x164+3+116
+$(IBASE): %-ibase.png: %-base.png
+ $(PIC)crop.sh $^ $@ $(CROP)
+
+# Convert the full-size icon images to 4-bit colour, because that
+# seems to work better than reducing it in 24 bits and then
+# dithering.
+$(IBASE4): %-ibase4.png: %-ibase.png
+ convert -colors 16 +dither -map $(PIC)win16pal.xpm $^ $@
+
+# Build the 24-bit PNGs for the icons, at three sizes.
+$(P48D24): %-48d24.png: %-ibase.png