Hi, sorry this seemed to slip through the cracks. I hope the information is
still useful to somebody.
You have the basic idea for how to write a multi-subimage file using the
ImageOutput interface, with the data just in a big array.
If I understand your question correctly, you want to use ImageBufAlgo:: crop()
to crop those images to a given ROI, but now you are stuck for how to write a
multi-image file (multi-part exr) for the resulting ImageBuf's.
Here's the outline of how you would do that:
// Start off the same way: you have your original images all in the big
'scratch' buffer,
// and an array of specs.
// Assume you want to crop them all to ROI 'cropped_roi'.
// Make a new set of specs with the cropped sizes
std::vector<ImageSpec> cropped_specs (orig_fb_count);
for (int s = 0; s < orig_fb_count; ++s) {
cropped_specs[s] = specs[s];
cropped_specs[s].set_roi (cropped_roi);
}
// Open an ImageOutput for multi-subimage as you did before
out->open (filename.toStdString(), orig_fb_count, cropped_specs.data());
// Crop each individual image and write it
unsigned int xoffset = 0;
for (int s = 0; s < orig_fb_count; s++) {
if (s > 0) { // Not needed for the first, which is already open
out->open (filename.toStdString(), cropped_specs[s],
ImageOutput::AppendSubimage);
}
// Make a light-weight ImageBuf that "wraps" your existing data.
ImageBuf uncropped (specs[s], scratch + xoffset);
// Crop it. (This will make a copy of just the cropped region.
ImageBuf cropped = ImageBufAlgo::crop (uncropped, cropped_roi);
// Write the new ImageBuf to the open file
cropped.write (out);
// Move to the next buffer position.
xoffset += specs[s].image_bytes();
// Note: the 'cropped' ImageBuf will automatically be destroyed and
// have its memory freed when it exits scope at the end of this loop.
}
> On Jun 3, 2020, at 6:24 AM, Sven Steinbauer <s...@themill.com> wrote:
>
> Hello,
>
> I've sent an email about this before but I think my reply got lost somewhere.
> Anyway, I am trying to crop a multi-image Exr file.
>
> I have managed to write out the multi-image like this (because
> out->supports("appendsubimage") returns false)
>
> out->open (filename.toStdString(), orig_fb_count, specs);
>
> // Write the individual subimages
> unsigned int xoffset = 0;
> for (int s = 0; s < orig_fb_count; s++) {
> if (s > 0) { // Not needed for the first, which is already open
> out->open (filename.toStdString(), specs[s],
> ImageOutput::AppendSubimage);
> }
> out->write_image (TypeDesc::BASETYPE(specs[s].format.basetype), scratch +
> xoffset);
> xoffset += specs[s].image_bytes();
> }
>
> Here the scratch is a scratch file buffer storing all the aovs contiguously,
> and the arrap of specs stores the spec for each one. This is working great,
> but I want to add an autocrop feature.
>
> I can calculate the ROI (or BBox) for the overall image, but I am not sure
> how to crop the images.
>
> The original code I inherited uses ImageBufAlgo::crop, and then
> ImageBuf::write to save the file. I am not sure how to write out the result
> from the crop to a multi-image EXR
>
> out->open (filename.toStdString(), orig_fb_count, specs);
>
>
> What's the correct method to crop the image and write it out as a multi-image
> EXR?
>
> SVEN STEINBAUER​
> Senior R&D Engineer
> T
> +44 20 7287 4041
> <http://www.themill.com/>
> SUPPORTING WORLD PRIDE MONTH 2020
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--
Larry Gritz
l...@larrygritz.com
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