I tried this myself and I couldn't get the file sizes that you were getting. Here's a list of the commands I was running:
wget http://joel.poloney.com/source.png convert -resize 426x320 -dither -colors 256 -depth 8 source.png resized.png pngcrush source.png crushed.png Here are my file sizes: crushed.png - 76,593 resized.png - 142,057 source.png - 87,833 Any ideas? -- Joel On Fri, Apr 25, 2008 at 9:30 AM, Ross Presser <[EMAIL PROTECTED]> wrote: > 1. Your source image is a 256-color palette image. If you resize any > image, by default the output will be in truecolor aka 24 bit color aka 8 > bits per pixel. You must quantize the image down to 256 colors. This > commandline resizes and quantizes, giving an output of 52,209 bytes: > > convert -resize 426x320 -dither -colors 256 -depth 8 source.png > resized.png > > 2. For even more compression, you can turn to pngcrush, not part of > imagemgick but a separate package. pngcrush applied to resize.png gave me an > output of 49,905 bytes. > > 3. Both convert and pngcrush will preserve the transparency in this case. > > > On Fri, Apr 25, 2008 at 3:31 AM, Joel Poloney <[EMAIL PROTECTED]> wrote: > >> 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 >> _______________________________________________ >> Magick-users mailing list >> [email protected] >> http://studio.imagemagick.org/mailman/listinfo/magick-users >> > > Greased Lightbox <http://shiftingpixel.com/lightbox/> →←+-↻ > > Loading image > > Click anywhere to cancel > > Image unavailable > >
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