On Wed, 06 Jan 2010 11:41:13 -0600, Programmer In Training wrote:

Why are the thumbnails larger in file size then most of the originals (at full size)?! This is unacceptable. I'd rather not use jpg if it can at all be avoided. I used the same exact settings for saving as a png that I used for the originals.

Your originals have few colours and sharp borders, and are fairly small. The thumbnails aren't that much smaller, but due to resizing, you introduced a lot of new colours, which make the images harder to compress, despite somewhat smaller size. You can save some space by converting the images (both original and resized) to 256 colours, but the originals will likely still compress better.

Programmer In Training wrote:

Thanks for the suggestions, but after converting to indexed and reducing to 256 colors, some of the original sized images were BIGGER in file size so I just wound up cropping out what I really didn't need for the article I'm writing (if anyone is interested in reading it, I'll provide a link if you mail me off list) and doing away with the idea of thumbnails completely (for some reason, all the reduced sized images, despite what I set the compression type to, look thoroughly crappy, which is a change from 2.6.6 (I'm using GIMP 2.6.8)). Hopefully none of the images will flow outside the boundry of the blog layout. I've also been having another issue with GIMP, but I think that one is because of Windows and not GIMP.

On Linux I use convert from the imagemagic suite. I just tried it on some pngs with -resize 150x and all of the outputs were smaller. YMMV.

Patrick

On Wed, 06 Jan 2010 13:25:26 -0600, Programmer In Training wrote:

Thanks for the suggestions, but after converting to indexed and reducing to 256 colors, some of the original sized images were BIGGER

I forgot to mention, you have to select "No dithering" (since these are screenshots, dithering only makes the images worse).

On Wed, 2010-01-06 at 14:42 -0600, Programmer In Training wrote:

I need to read up on the GIMP documentation regarding PNG quality settings. Mine are apparently too high.

PNG is a lossless image format, it doesn't have any quality settings. The only thing you can adjust is the compression factor. A higher compression factor will result in the same image at smaller file size traded in for longer compression and decompression times.

Sven

On Wed, 06 Jan 2010 14:42:12 -0600, Programmer In Training wrote:

I did, after the first time I converted them. I reconverted back to RGB, then back to Indexed with no dithering.

Converting a dithered indexed image to RGB doesn't remove dithering. You have to convert the original RGB image to indexed with no dithering.

I need to read up on the GIMP documentation regarding PNG quality settings. Mine are apparently too high.

you may always use maximum compression doesn't change quality

on RGB images usually png have a quite bigger file size then jpg, but if indexed file size should be not bigger of a corresponding gif

BUT in the past i had problem to save on gimp -windows indexed png, for some reason file size was not different then saving them as rgb.

Not sure if that was a issues of whatever version of gimp i was using then,now i found quicker do all scaling and conversion with Xnview

(that on windows is the tool for the trade, a bit as imagemagick on linux, but offer also a friendly interface...alas is not free source, just free )