My first guess would be that KSnapshot made an indexed image and GIMP and ImageMagick are saving it as RGB. That shouldn't happen though.

Check the compression level.

It could just be that KSnapshot is better at making PNGs. But I would be surprised because GIMP and ImageMagick are both very good.

Cheers, Daniel.

On Sun, Nov 30, 2003 at 06:10:50PM -0500, Bob Lockie wrote:

I have a screen capture that I did with KSnapshot that is 34108 bytes. I shrunk it down with gimp (and ImageMagick) and it got a lot larger (78875 byte).

Does anyone know what could be happening to make smaller images larger? I did some screen captures for a manual I am writing but I want to make the file sizes smaller.

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On Mon, Dec 08, 2003 at 04:43:43PM -0500, Bob Lockie wrote:

KSnapshot: 34 108 bytes, 585x385, 24bbp, RGB, deflate. Gimp: 78 896 bytes, 400x263, 24bbp, RGB, deflate, compression 9.

There are no options in KSnapshot so I don't know what the compression level is (can it be higher than the highest in Gimp=9?).

I think 9 is the highest possible in zlib.

Anyway, if no one has said it yet, this is most probably caused by you scaling the image with resampling turned on. This makes images less easy to compress when using the types of compression that PNG and such use.

How about you put the images online somewhere so we can be sure of this?

Marco

On Mon, Dec 08, 2003 at 06:13:47PM -0500, Bob Lockie wrote:

The pics are on the web at:

http://www.lockie.ca/test/ksnapshot.png http://www.lockie.ca/test/gimp.png

Ugh, KDE is ugly.. *ducks*

Anyway, this is exactly what I said. When you rescaled the image you made it harder to compress because of the resampling. Therefore the filesize is higher.

Someone more of an expert in compression methods can tell you more about this, I don't dare get into it too deeply.

Marco

On Mon, Dec 08, 2003 at 06:13:47PM -0500, Bob Lockie wrote:

On 12/08/03 16:57 Marco Wessel spoke thusly

On Mon, Dec 08, 2003 at 04:43:43PM -0500, Bob Lockie wrote:

KSnapshot: 34 108 bytes, 585x385, 24bbp, RGB, deflate. Gimp: 78 896 bytes, 400x263, 24bbp, RGB, deflate, compression 9.

There are no options in KSnapshot so I don't know what the compression level is (can it be higher than the highest in Gimp=9?).

The pics are on the web at:

http://www.lockie.ca/test/ksnapshot.png http://www.lockie.ca/test/gimp.png

As Marco speculated earlier (and you cut out):

Anyway, if no one has said it yet, this is most probably caused by you scaling the image with resampling turned on. This makes images less easy to compress when using the types of compression that PNG and such use.

That's exactly what is happening. Zoom in on your gimp.png and you'll see shades of gray around your letters. Since there's more color variance in your scaled down picture, there's less common information to compress with, so the picture is larger.

You can try setting the interpolation type to None, which will simply throw out data instead of trying to interpolate the pixel data, but the results are pretty poor. You do get a smaller file size though.

I will note, that loading ksnapshot.png and saving it in the GIMP (without scaling) results in a smaller file size, so KSnapshot isn't doing as well as it could. ;)

in a smaller
-Yosh