--- On Sun, 7/18/10, Uli Schlachter <[email protected]> wrote: > From: Uli Schlachter <[email protected]> > Subject: Re: awesome-3.4.6 patch: error convert: Ignoring incorrect gAMA value > To: [email protected] > Cc: [email protected] > Date: Sunday, July 18, 2010, 6:21 PM > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > Am 18.07.2010 13:42, Vinay Pawar wrote: > > Hi, > > > > Using awesome-3.4.6, with libpng-1.2.42 and > ImageMagick-6.5.6 > > > > Following is a little patch that fixes the > error(ignorable) i get at build time. > > > > '-gamma 0.6' was added for old ImageMagick > compatibility but appears to be interfering with the new > versions. Also newer ImageMagick-6.5.5 onwards there's a new > -auto-gamma which could be used in the future. > > > > The 'incorrect gamma=(0/100000)' error is returned by > libpng, use 'display -verbose <bad-generated-png>' to > check sanity of image. > > > > 'convert -gamma 0.6 -channel A -evaluate Multiply 0.4 > <image> <new-image>' > > 'convert -auto-gamma -channel A -evaluate Multiply 0.4 > <image> <new-image>' > > 'convert -channel A -evaluate Multiply 0.4 > <image> <new-image>' > > > > All 3 above commands produce the same image visually. > Either '-auto-gamma' should be used or '-gamma' should be > dropped. > > Sorry, but the resulting images do look different. > I grabbed the titlebar icons from the default theme, moved > them into their own > dir and ran this uglyness: > > for img in *png > do > for x in '-gamma 0.6 -channel A -evaluate Multiply > 0.4' '-channel A -evaluate > Multiply 0.4' '-auto-gamma -channel A -evaluate > Multiply 0.4' '-evaluate Pow 2 > -channel A -evaluate Multiply 0.4' > do > convert "$img" $x "$img: $x.png" > done > done > > I then viewed the result with 'feh --index .'. > > My findings are that especially no gamma option and > '-auto-gamma' produce > different images than what got now. This leaves us with > '-gamma 0.6' which is > what we are currently using and '-evaluate Pow 2' which was > used before, but was > dropped for compatibility with newer ImageMagick. > > Cheers, > Uli >
You can use 'display -identify -verbose <image-file>' and use it's output for comparison. I find they produce the same result. -- zoyd -- To unsubscribe, send mail to [email protected].
