On 24 Feb 2014, at 18:04, Bill Dudney <[email protected]> wrote: > > Make sure that what you are looking at is what you think you are looking at. > When you look at it in Preview is it being scaled? If so then the default > scaling algorithm in Preview for TIFF might be 'fast but ugly’ (I don’t know, > just guessing). With a PNG it might be choosing a ‘nice but slower’ algorithm. > > My recommendation would be to ensure you are looking at the image unscaled as > both PNG and TIFF. In Preview I think the menu item is ‘Show Full Size’ or > something like that.
I'd already done that, but doing it again made me realize that the problem is 100% associated with the alpha channel. Where the pixels are fully opaque everything is fine. Where pixels are semi-transparent is where the problem occurs. Fully transparent is also fine. I wonder if the problem is to do with premultiply. Does TIFF deal with an image generated from a premultiplied bitmap properly? > If the docs are vague it would help to file a bug > (http://bugreporter.apple.com) to make sure the people in charge of those > docs get your input. I wrote a bug report ages ago relating to the ImageIO documentation when I had the same problem understanding the settings when creating gif animations using CGImageDestination. I've not had any response to that bug report. Thanks for the help. Kevin _______________________________________________ Cocoa-dev mailing list ([email protected]) 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: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
