I've been banging my head against this all night and can't come up with any
solution. I'm trying to take a PNG image, resize it, and compress it (if I
can). The PNG image I'm working with has transparency. You can find it here:
http://joel.poloney.com/source.png. I have imagemagick version 6.2.4.
The source png is 85kb. If I run the command "convert -compress JPEG
-quality 80 source.png output.png", the output.png is about 118kb.
Obviously, that didn't work. Say I want to resize this image down before I
compress it. The original size of this is 600x450. If I run the command
"convert -resize 426x320 source.png resized.png", the resized.png is about
150kb. Why is my image smaller pixel-wise and bigger file-size wise?
I then began experimenting with image masks. I figured, if I could extract
out the alpha channel into a 8-bit mask.png ("convert source.png -channel
matte -negate -separate -depth 8 -type Grayscale mask.png"). I then
converted the png to a jpeg and compressed the jpeg. I finally composed the
two back together with the "-compose Copy_Opacity" option, and it works...
but the file size is enormous.
If I use the original source png in Flash CS3 and create a simple movie with
1 frame (the source.png), and export it (with a jpeg compression of 80), the
resulting swf is 37.1kb. They're doing some kind of compression and I can't
figure out what it is and why it's not working with imagemagick.
Any suggestions?
Thanks,
-- Joel
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