Re: [Openexr-devel] Writing scanline at a time

[Florian Kainz]

Charles Henrich wrote:
> 
> >       for (int y = 0; y < height; ++y)
> >       {
> >           for (int x = 0; x < width; ++x)
> >           {
> >               g[x] = ...;
> >               z[x] = ...;
> >
> >               file.writePixels (height);
> >           }
> >       }
> 
> Im thinking that file.writePixels(height) is meant to be in the outerloop
> yeah?  This would be a good sample for the web pages!
> 
> -Crh
> 
>        Charles Henrich                                   address@hidden
> 
>                          http://www.sigbus.com/~henrich

You are correct; writePixels should be in the outer loop.  Also, the
argument to writePixels should be 1, not height.  Looking at the example
just now, I noticed a few more errors (I was in a bit of a hurry yesterday).
Here's a corrected version:


    void
    writeImage (const char fileName[], int width, int height)
    {
        //
        // Open an image file by creating an OutputFile object.
        // The image file will contain two channels, G, of type
        // HALF, and Z, of type FLOAT.
        //

        Header header (width, height);                                    
        header.channels().insert ("G", Channel (HALF));                   
        header.channels().insert ("Z", Channel (FLOAT));                  

        OutputFile file (fileName, header);                               

        //
        // Allocate memory to hold one scan line.
        //

        vector<half>  gPixels (width);
        vector<float> zPixels (width);

        //
        // Create a FrameBuffer object that tells the OutputFile
        // where to find the pixels for our image.  Note that yStride
        // is 0, which means that all scan lines live at the same
        // memory address.
        //

        FrameBuffer frameBuffer;                                          

        frameBuffer.insert ("G",                              // name   
                            Slice (HALF,                      // type   
                                   (char *) &gPixels[0],      // base   
                                   sizeof (gPixels[0]),       // xStride
                                   0));                       // yStride

        frameBuffer.insert ("Z",                              // name   
                            Slice (FLOAT,                     // type   
                                   (char *) &zPixels[0],      // base   
                                   sizeof (zPixels[0]),       // xStride
                                   0));                       // yStride

        file.setFrameBuffer (frameBuffer);                                

        //
        // Generate the image one scan line at a time,
        // and store each scan line in the file immediately.
        //

        for (int y = 0; y < height; ++y)
        {
            for (int x = 0; x < width; ++x)
            {
                gPixels[x] = ...;
                zPixels[x] = ...;
            }

            file.writePixels (1);
        }
    }