2001.02.21 18:05 "PhotoShop alpha channels and LibTiff", by Chris Losinger

i have a TIFF created in PhotoShop (vers??). it is saved with an alpha channel.

when i go to read this image using TIFFReadRGBAImage, the alpha channel is not read. LibTiff treats it as an RGB image, not an RGBA.

tracing the code, i found that the alpha channel is marked: EXTRASAMPLE_UNSPECIFIED. when i forced that flag to EXTRASAMPLE_ASSOCALPHA, LibTiff returns the proper alpha channel.

what to do about this?

is it a photoshop bug or a libtiff bug?

-c