Apple icon bullshit

Apple introduced a bug in macOS 11 that they can't be arsed to fix which
breaks PNG loading into icns files by dropping the blue channel of the
last pixel, leaving a streak of yellow pixels at the bottom of the
image.

This hacks around it by setting a fully transparent, non-white (actually
yellow) pixel in the bottom-right corner of the images.

This is such inexcusable trash.

contrib/macos/mk-icns.sh

@@ -7,10 +7,69 @@ outdir="${out/%.icns/.iconset}"
 
 set -e
 
+# Apple's PNG encoding/decoding is buggy and likes to inject yellow lines, particularly for the
+# smaller images.  This is apparently a known issue since macOS 11 that apple just doesn't give a
+# shit about fixing (https://en.wikipedia.org/wiki/Apple_Icon_Image_format#Known_issues).
+#
+# So moral of the story: we have to arse around and edit the png to put a tranparent pixel in the
+# bottom-left corner but that pixel *must* be different from the preceeding color, otherwise Apple's
+# garbage breaks exposing the dumpster fire that lies beneath and drops the blue channel from the
+# last pixel (or run of pixels, if they are the same color (ignoring transparency).  So, just to be
+# consistent, we make *all* 4 corners transparent yellow, because it seems unlikely for our logo to
+# have full-on yellow in the corner, and the color itself is irrelevant because it is fully
+# transparent.
+#
+# Why is there so much broken, buggy crap in the macOS core???
+
+no_r_kelly() {
+    size=$1
+    last=$((size - 1))
+    for x in 0 $last; do
+        for y in 0 $last; do
+            echo -n "color $x,$y point "
+        done
+    done
+}
+
+
+
 mkdir -p "${outdir}"
-for size in 16 32 64 128 256 512 1024; do
-    convert -background none -resize "${size}x${size}" "$svg" -strip "png32:${outdir}/icon_${size}x${size}.png"
+for size in 32 64 128 256 512 1024; do
+    # Yay Apple thanks for this utter trash OS.
+    last=$((size - 1))
+    convert -background none -resize "${size}x${size}" "$svg" \
+        -fill '#ff00' -draw "$(no_r_kelly $size)" \
+        -strip "png32:${outdir}/icon_${size}x${size}.png"
 done
+
+
+# Outputs the imagemagick -draw command to color the corner-adjacent pixels as half-transparent
+# white.  We use this for the 16x16 (the others pick up corner transparency from the svg).
+semitransparent_off_corners() {
+    size=$1
+    for x in 1 $((size - 2)); do
+        for y in 0 $((size - 1)); do
+            echo -n "color $x,$y point "
+        done
+    done
+    for x in 0 $((size -1)); do
+        for y in 1 $((size - 2)); do
+            echo -n "color $x,$y point "
+        done
+    done
+}
+
+# For 16x16 we crop the image to 5/8 of its regular size before resizing which effectively zooms in
+# on it a bit because if we resize the full icon it ends up a fuzzy mess, while the crop and resize
+# lets us retain some detail of the logo.  (We don't do this for the 16x16@2x because that is really
+# 32x32 where it retains enough detail).
+convert -background none -resize 512x512 "$svg" -gravity Center -extent 320x320 -resize 16x16 \
+    -fill '#ff00' -draw "$(no_r_kelly 16)" \
+    -fill '#fff8' -draw "$(semitransparent_off_corners 16)" \
+    -strip "png32:$outdir/icon_16x16.png"
+
+# Create all the "@2x" versions which are just the double-size versions
+rm -f "${outdir}/icon_*@2x.png"
 mv "${outdir}/icon_1024x1024.png" "${outdir}/icon_512x512@2x.png"
 for size in 16 32 128 256; do
     double=$((size * 2))