Convert OpenEXR write image code to OpenimageIO

[LaZyLinh]

Hi, I currently have this code

void saveEXR(const char* filename, int width, int height, const float* data,
             const float* rangeMod,
             float pixelSpacing, float frequency, float antLen, float
             rangeScale, float rangeCenter){
    Header header (width, height);
    header.insert("pixel spacing", FloatAttribute (pixelSpacing));
    header.insert("frequency", FloatAttribute (frequency));
    header.insert("antenna length", FloatAttribute (antLen));
    header.insert("range scale", FloatAttribute (rangeScale));
    header.insert("range center", FloatAttribute (rangeCenter));
    header.channels().insert ("G", Channel (FLOAT));
    header.channels().insert ("Z", Channel (FLOAT));
    OutputFile file (filename, header);
    FrameBuffer frameBuffer;
    frameBuffer.insert ("G", Slice(FLOAT, (char *)data, sizeof(*data),
                                   sizeof(*data)*width));
    frameBuffer.insert ("Z", Slice(FLOAT, (char *)rangeMod,
                                   sizeof(*rangeMod),
                                   sizeof(*rangeMod)*width));
    file.setFrameBuffer(frameBuffer);
    file.writePixels(height);

How would I convert this to OIIO syntax for writing OpenEXR files? I'm doing this in C++!

Thank you!

[lgritz]

It would look something like this:

ImageSpec spec (width, height, 2, TypeFloat);
spec.channelnames[0] = "G";
spec.channelnames[1] = "Z";
spec["pixel spacing"] = pixelSpacing;
spec["frequency"] = frequency;
... rest of attributes ...
auto file = ImageOutput::create(filename);
file->open(filename, spec);
file->write_image(TypeFloat, buffer);

But there's one catch... there's not currently a way to make it pull the "G" channel from one buffer and the "Z" channel from a totally different buffer. It expects the pixels to be "contiguous", so you need to first copy your data around to get a single buffer that looks in memory like "GZGZGZGZ...".

There is probably a good argument to be made that we should add read/write API calls that let you specify the buffer pointer and strides per channel, but currently we don't have that. It's not something I recall people asking for very frequently.