[Gimp-user] Rotate increases PNG size x10 !
People, I used: xsane-0.997-3.fc12.x86_64 to scan an A4 page at 300dpi in LineArt mode and got a file of: 325,668 t_xsane.png I then edited it using: gimp-2.6.8-1.fc12.x86_64 rotating the image by -0.7 and cropping slightly - the resulting image was 10 times the size!: 3,368,891 t_xsane_-0.7.png As another test I simply opened the original file and saved it with a new name - this gave about a 33% increase in size: 478,305 t_xsane_nochange.png What is going on with these size increases? Thanks, Phil. -- Philip Rhoades GPO Box 3411 Sydney NSW 2001 Australia E-mail: p...@pricom.com.au ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] Rotate increases PNG size x10 !
On Wed, Jun 23, 2010 at 8:07 PM, Philip Rhoades p...@pricom.com.au wrote: What is going on with these size increases? It may be that after rotation, pixels that were otherwise the same color got anti-aliased and were slightly different color. This would increase the image size. Can you show us the original scan? Regards, -- Branko Vukelić bg.bra...@gmail.com stu...@brankovukelic.com Check out my blog: http://www.brankovukelic.com/ Check out my portfolio: http://www.flickr.com/photos/foxbunny/ Registered Linux user #438078 (http://counter.li.org/) I hang out on identi.ca: http://identi.ca/foxbunny Gimp Brushmakers Guild http://bit.ly/gbg-group ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] Rotate increases PNG size x10 !
On Thu, 24 Jun 2010 06:04:57 am Branko Vukelic wrote: On Wed, Jun 23, Philip Rhoades wrote: What is going on with these size increases? It may be that after rotation, pixels that were otherwise the same color got anti-aliased and were slightly different color. This would increase the image size. Branco, that may account for the increased size of a _rotated_ image, but Phil also increased the size simply during a re-save of an unchanged image. Phil, I suspect that when re-saving that image, you may wish to check the Advanced Settings popup to ensure that the PNG compression ratio is set to maximum at the time. WRT the rotated image, it wouldn't so much be anti- aliasing as that the rotation is unlikely to be precisely right-angled, so pixels along edges would be partially coloured, which would make the PNG compression process less efficient. If the image is text or something else essentially monochrome, Phil might try desaturating, then (regardless of desat) Auto/Stretch Contrast. This should minimise colour-gradient effects somewhat, so provide for more effective compression. If minute details are not so important, saving as JPeG will reduce the size massively without serious loss of visual quality. Loss of quality can be adjusted to a reasonable compromise level within the JPeG settings during SaveAs. Cheers; Leon ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
Re: [Gimp-user] Rotate increases PNG size x10 !
On Wed, Jun 23, 2010 at 5:30 PM, Leon Brooks leon-g...@cyberknights.com.au wrote: If the image is text or something else essentially monochrome Or image-mode, bitmap, 1-bit palette should drastically reduce the file size. I suspect that the 'line art' setting in xsane is producing a grayscale image but with each pixel either solid black or solid white, which would make the resulting PNG easy to compress. Rotating likely causes many pixels to become shades of gray along the edges and increasing the file size. My scanner is dead or I'd test this out myself. Not sure on the increase when saving the image as-is - are all of the 'Save Comment', 'Save Creation', etc. boxes unchecked in the PNG save dialog? Chris ___ Gimp-user mailing list Gimp-user@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
