[PDFBOX-5526] Adding subsampling for masks

[velyan]

See Jira ticket

When PDImageXObject.getImage() gets invoked with subsampling and region, internally it loads the entire mask into memory:

pdfbox/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/graphics/image/PDImageXObject.java

Line 465 in 961c052

softMask.getOpaqueImage(), softMask.getInterpolate(), true, extractMatte(softMask));

and applies the entire mask on the subsampled image.

Which is extra work and can cause OOM exceptions.

The proposed optimisation is to pass region and subsampling params to PDImageXObject.getOpaqueImage() here -

pdfbox/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/graphics/image/PDImageXObject.java

Line 548 in 961c052

public BufferedImage getOpaqueImage() throws IOException

such that masks are also subsampled before applying them...

[THausherr]

You're not passing the region despite having it as a parameter

[velyan]

You're not passing the region despite having it as a parameter

Thanks, fixed!