Re: [Openexr-devel] C API calls

[Thomas Lock]

I finally got it to work in debug mode, which exposed an error that wasn't
coming up in release mode (not sure why). It was missing 1 library file to
link to. I'm going to get reading and writing to work first in debug mode
and then worry about release mode.
At this point i have the writing working (verified with 2 other apps), but
the reading seems to have a non-fatal error (image is black but correct
dimensions). I don't think the buffer is getting filled properly. This
function is simply the opposite of what the writing function does, so once
the buffer is filled and converted to my array the rest is done outside this
function. I added the lines of code i believe the problem is related to, but
i can't seem to find any documentation on the C API so i am guessing.

ImfRgba *rgba;

rgba = (ImfRgba *)malloc(width * height * sizeof(ImfRgba));

header = ImfInputHeader(fp);

ImfHeaderDataWindow(header,&x1,&y1,&x2,&y2);

ImfInputSetFrameBuffer(fp, rgba , 1, width);

ImfInputReadPixels(fp, height, 0 );



----- Original Message ----- 
From: "Florian Kainz" <address@hidden>
To: "Thomas Lock" <address@hidden>
Cc: <address@hidden>
Sent: Thursday, July 20, 2006 12:05 AM
Subject: Re: [Openexr-devel] C API calls


> What does "fail" mean in this case?  Does the application crash?
> If it does, have you tried using a debugger to get a stack trace?
>
> Does ImfOpenOutputFile return a null pointer?  If you do get a null
> pointer, have you tried calling ImfErrorMessage() to find get some
> diagnostic output?  Your example contains no error checking code.
> Unlike the C++ interface, the C interface does not throw exceptions;
> you must explicitly check the return values of the functions you call.
>
> Thomas Lock wrote:
> > Hi Drew
> >
> >              I completely rewrote my code to meet the C API calls. This
time
> > i get zero warnings or errors but the app specifically fails on this
call
> > "file = ImfOpenOutputFile(filenames, header, IMF_WRITE_RGBA );". I tried
a
> > variety of filename options and nothing seems to work. I can't verify if
my
> > remaining code works, but i believe it is correct.
> >
> > extern "C" void WINAPI writeOpenEXR (char *filename, int width, int
height,
> > float* Bits128)
> > {
> >         int LineWidth=width*4;
> >         float fwidth;
> >         const char fileName[] = "c:\foo2.exr";
> >         const char *filenames = "c:\foo2.exr";
> >
> >         ImfOutputFile *file;
> >         ImfRgba *base;
> >         base = (ImfRgba *)malloc(width * height * sizeof(ImfRgba));
> >         fwidth = (float)width;
> >         ImfHeader *header;
> >         header = ImfNewHeader();
> >         ImfHeaderSetDisplayWindow(header, 0, 0, width - 1, height - 1);
> >         ImfHeaderSetDataWindow(header, 0, 0, width - 1, height - 1);
> >         ImfHeaderSetScreenWindowWidth(header, fwidth);
> >         file = ImfOpenOutputFile(filenames, header, IMF_WRITE_RGBA );
> >
> >         ImfDeleteHeader(header);
> >
> >         for(int h=0;h<height;h++)for(int b=0;b<width;b++)
> >        {
> >             ImfHalf half;
> >
> >             int i=h*LineWidth+(b<<2);
> >             int j=h*LineWidth+b;
> >
> >             ImfFloatToHalf(Bits128[i], &half);
> >             base[j].b = half;
> >
> >             ImfFloatToHalf(Bits128[i + 1], &half);
> >             base[j].g = half;
> >
> >             ImfFloatToHalf(Bits128[i + 2], &half);
> >             base[j].r = half;
> >
> >             ImfFloatToHalf(Bits128[i + 3], &half);
> >             base[j].a = half;
> >         }
> >
> >         ImfOutputSetFrameBuffer( file, base, 1, width );
> >         ImfOutputWritePixels(file, height );
> >         ImfCloseOutputFile(file);
> >
> >         free(base);
> > }
> >
> >
> >
> >
> > _______________________________________________
> > Openexr-devel mailing list
> > address@hidden
> > http://lists.nongnu.org/mailman/listinfo/openexr-devel
> >
> >
>