Added mktrans to scripts

scripts/scripts/mktrans

@@ -0,0 +1,147 @@
+#!/bin/bash 
+# B9 June 2017
+
+# mktrans 
+# This is similar to ImageMagick's bg_removal script, but much higher
+# quality. (It's also faster and simpler to use.) 
+#
+# For a sample, run these commands:
+#    convert logo: logo.png
+#    mktrans logo.png
+#    display logo-transparent.png
+
+
+# Fuzz is how far off the background color can be (in percent).
+# This is important for getting good antialiasing.
+defaultfuzz=20
+
+usage() {
+    cat <<EOF
+
+mktrans: Convert images into shaped transparent pngs by floodfilling
+	 the background with transparency (antialiased alpha channel).
+	 Unless a different starting pixel is specified, the top left
+	 pixel is used as the "background" color to remove and
+	 floodfill starts from all four image edges,
+
+Typical usage: 
+
+	mktrans foo.jpg		(creates foo-transparent.png)
+
+Usage: mktrans  [-f <fuzz>]  [-s|-S]  [-p <x>,<y>]  [-v]  <files ... >
+
+	-f <fuzz>: How loosely to match the background color (default $defaultfuzz%)
+
+    	   	   Advanced options:
+	       -s: Use speedy antialiasing (much faster, slightly less acurate) 
+	       -S: Supress antialiasing completely. (Useful for repeated runs)
+	p <x>,<y>: Floodfill from pixel at x,y instead of 0,0
+	       -v: Verbose
+EOF
+
+# * Side note: This creates an antialiased (blurred) alpha channel
+#   that is also eroded by half a pixel to avoid halos. ImageMagick's
+#   morphological operations don't (yet?) work at the subpixel level,
+#   so I'm blowing up the alpha channel to 200% before eroding. Since
+#   this can be slow on large images, consider using the '-s' option
+#   which uses a faster, lower quality antialiasing.
+
+# * Running this script on an image that already has transparency will
+#   erode the image due to the antialiasing. Using -S is a workaround,
+#   but is not very satisfactory. Perhaps this script should remove any
+#   existing transparency before manipulating the image and then add it
+#   back in at the end. But then again, how often are people going to
+#   want to do that? The only use I can think of is when using -p.
+
+# * Because of the previous bug, if you do use -p to fill lots of
+#   lagoons, you'll probably want to use -A at the same time.
+
+# * Finding the coordinates for -p is a pain. It'd be nice if there was
+#   a -P option which let the user click on a point (or multiple points)
+#   in the image to start the floodfill.
+
+    exit 0
+}
+
+fuzz=$defaultfuzz
+pixelcomma="0,0"
+pixelplus="+0+0"
+
+while getopts f:sAShp:v name; do
+    case $name in
+        f) fuzz=$OPTARG
+           ;;
+        s) sflag=True
+           ;;
+        S|A) noantialias=True
+           ;;
+        v) vflag=True
+           ;;
+        h) usage
+           ;;
+        p) pixelcomma=$OPTARG
+           pixelplus=+${OPTARG%,*}+${OPTARG#*,}
+           pflag=True
+           ;;
+        *) usage
+           ;;
+    esac
+done
+
+shift $((OPTIND-1))
+[[ "$#" != 0 ]] || usage
+
+
+for filename; do
+    # Get color of 0,0 (top left) pixel
+    color=$(convert "$filename" -format "%[pixel:p{$pixelcomma}]" info:-)
+    if [[ "$color" == *rgba*",0)" ]]; then
+	color="${color%,0)},1)"	# Floodfill only works with opaque colors.
+    fi
+    if [[ "$color" == "none" ]]; then
+	echo "Error: $filename: pixel at $pixelcomma is completely transparent. Cannot floodfill." >&2
+	continue
+    fi
+
+    options=""
+    if [ -z "$pflag" ]; then
+	# Add a 1 pixel border so we'll fill from the bottom and sides as well.
+	options+=" -bordercolor $color -border 1 "
+    fi
+    # In a new stack, make a copy of the image
+    options+=" ( +clone "
+    # [copy] floodfill with transparency ("none") starting at top-left
+    options+="		-fuzz $fuzz% -fill none -floodfill $pixelplus $color"
+    # [copy] extract just the transparency (alpha channel)
+    options+="		-alpha extract"
+
+    if [ -z "$noantialias" ]; then
+	if [ -z "$sflag" ]; then
+            # [copy] blow up the alpha channel so we can do sub-pixel morphology
+            options+="	-geometry 200%"
+            # [copy] blur the alpha channel to make it antialiased
+            options+="	-blur 0x0.5"
+            # [copy] shrink the region that is opaque by half a pixel.
+            options+="	-morphology erode square:1"
+            # [copy] scale the alpha channel back to normal size.
+            options+="	-geometry 50%"
+	else	# sflag: speedy antialias
+            # [copy] blur the alpha channel to make it antialiased
+            options+="	-blur 0x1"
+            # [copy] only antialias inside the figure (<50% opacity becomes 0%)
+            options+="	-level 50%,100%"
+	fi
+    fi
+    # [copy] end the stack.
+    options+=" ) "
+    # Compose the original image and the copy's alpha channel.
+    options+=" -compose CopyOpacity -composite"
+    if [ -z "$pflag" ]; then
+	# Remove the 1 pixel border we added
+	options+=" -shave 1"
+    fi
+    
+    [ "$vflag" ] && echo convert "$filename" $options "${filename%.*}-transparent.png"
+
+    convert "$filename" $options "${filename%.*}-transparent.png"
+done