resize image without losing quality with Gimp

Question

i have a bunch of images which are way too big i need to decrease their size from 30 kb to 10 or 5 kb without loosing quality. I tried to change the dpi and pixels with no succeed. The images got blurred, and as they have text i can't read anything after the changes. Is there anyway i can accomplish this without loosing quality? I have almost a dozen images in my application.

Thanks in advance and have a nice day.

Answer 1

for batch resizing I use IrfanView (despite it's "lite-ness" it's very powerful). It has a nice batch dialog, with a lot of options.

If you're working with png files try using better compression, and/or different color depth settings (if you're not using transparency you could try converting them to jpeg, although you might lose some quality)

changing color depth/range/compression might not affect image quality (not visibile anyway, if used with moderation) and it will decrease the size of the picture - in most of the cases anyway

if you want to stick to Gimp (I never personally used it), it should have some export features where you can select some settings for the image, like format and options

Answer 2

You cannot leave out data without reducing quality. Data has meaning.

You may try to use improved compression, pngcrush is the tool that automatically tries several approaches for you and picks the best.

Reducing colour depth will reduce the file size (while reducing colour quality). You can also turn on dithering in some image editors, but that's another loss in quality.

If your image has photographic content rather than graphical, convert to JPEG and use the JPEG quality settings, experiment with them a bit.