Why '.png' files produced by ImageMagick are so much bigger than '.jpg' & '.gif' files?

Posted by Nick Gorbikoff on Stack Overflow See other posts from Stack Overflow or by Nick Gorbikoff
Published on 2010-04-21T21:31:01Z Indexed on 2010/04/21 21:33 UTC
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Filed under:

image-processing

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imagemagick

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jpg

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png

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gif

Hello.

I'm using ImageMagick to convert some files from one format to another. I was always under the impression that .png files were supposed to be as big/small as .jpg if not smaller, and definitely smaller than .gif.

However when I run

convert photo.jpg photo.png

The files I'm getting out is about 6 times bigger than the original jpg.
Original jpg is a regular photo about 300x500 px, 52 kb. Output is a proper png of the same dimensions, but size is about 307 kb?

Does anyoone know what the hack is going on? Am I doing something wrong?

P.S.:

I tried both on Debian and Windows with the same results.

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