On Nov 13, 2011, at 12:34 PM, Quincey Morris wrote: > On Nov 13, 2011, at 11:11 , James Merkel wrote: > >> This is kind of interesting -- if I rotate the image in Preview (rather than >> Image Capture), then the histogram looks normal. >> Looking at the NSBitmapImageRep from Preview image, the order is RGBA and >> there is no reported alpha channel. >> Furthermore for the Preview rotated image, the Exif Orientation tag says >> normal (horizontal), and the width and height are reported correctly. >> For the Image Capture rotated image, the Exif Orientation tag says rotated >> 90 degrees and the width and height are reversed (i.e. not reported >> correctly). >> I think Preview is doing the right thing and Image Capture is doing the >> wrong thing. >> Why I get a bad histogram from the IMage Capture rotated image I'm not sure. > > The implication of this is likely that you're misinterpreting the pixel > format of the Image-Capture-rotated image. (For example, did it change the > component values from 8-bit to 16-bit components or to floats, or something > like that?). In principle, it shouldn't be too hard to resolve. Simply > examining the data, or substituting a test image with known, > predictably-arranged colors, should let you see why your histogram > calculation doesn't match.
NSBitmapImageRep reports that the image is 32-bits per pixel, 8-bits per sample and the pixel values are integers. I have tried some simple one-color test images created in Photoshop Elements. They produce correct histograms. The Photoshop test images are 24-bits per pixel. I'm not sure I have control over making them 32-bits with an alpha channel. I'll have to look into it. Jim Merkel _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
