Typo in the last message, the flag set is TGA_ALPHA_USEFUL.
On 4/24/2013 1:30 PM, Lerenard Michel wrote:
I found why OIIO finds two channels in the file. The tga_alpha_type of
the file has been set to TGA_ALPHA_UNDEFINED_RETAIN.
I do not know how TGA works, I then have a question: what is the use
of such a flag ? How is it set ? Can i ignore it ?
To be able to load correctly this type of file (ie discard the alpha
layer), i have to parse the data buffer returned by OIIO, and it costs
quite some time. I there another way to detect such an empty channel
before calling "read_scanlines" which i use ?
2013/4/24 Michel Lerenard <[email protected]
<mailto:[email protected]>>
Hi,
I've spotted a weird behavior when opening grayscale files, i'm
wondering if I have to check something else in the header or if it
is the correct behavior: the ImageSpec structure tells me there
are two channels in the file, one called 'I' and another called
'A', which is absolutely black. (ie empty ?)
The file i'm opening is a simple black and white TGA used as a
mask, with, according to Gimp, photoshop, xnview, etc... a single
color channel. ( 8 bits )
Is there a way to check if a given channel is empty ? Apparently
the file does not hold any data for alpha, so i'm wondering if
OIIO is creating an alpha channel for compatibility and if I
should check some attributes to detect if there is actually any
data in it ?
Thanks for your help.
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