[
https://issues.apache.org/jira/browse/PDFBOX-4137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16386366#comment-16386366
]
Tilman Hausherr commented on PDFBOX-4137:
-----------------------------------------
Thanks; I ran my tests.
gs-bugzilla692689.pdf and several other files throw an
ArrayIndexOutOfBoundsException exception at 50% and 100% zoom in PDFDebugger,
but not at 25% or 200% or 400%.
I suspect that you should check for {{(x >= startx + scanWidth)}} below this
code and then break if needed:
{code}
if (x < startx || (x % subsampling) > 0)
{
x++;
{code}
PDFJS-4575-noimagedim.pdf brings a NegativeArraySizeException. There is a check
in getRGBImage() which would throw an IOException but that one has been
disabled by the change.
The subsampling feature should be optional. I suggest an option in PDFRenderer,
e.g. {{setSubsamplingAllowed}} and {{isSubsamplingAllowed}} and have it
disabled by default in 2.* and enabled in the trunk, and advertise the feature
in the FAQ. I will also look in Stackoverflow for answers that complain about
memory.
Yes, caching makes sense. We could remember the subsampling value and compare
with the current one.
> Allow subsampled/downscaled rendering of images, and rendering subimages
> -------------------------------------------------------------------------
>
> Key: PDFBOX-4137
> URL: https://issues.apache.org/jira/browse/PDFBOX-4137
> Project: PDFBox
> Issue Type: Improvement
> Components: Rendering
> Affects Versions: 2.0.8
> Reporter: Itai Shaked
> Priority: Minor
> Attachments: 0001-Image-render-subsample.patch,
> 0001-Image-rendering-subsampling-removed-metadata-options.patch, 067445.pdf,
> image_rendering_subsampling_hack.patch, large-jpeg.pdf
>
>
> Suggested/contributed change to allow subsampling of images and rendering
> sub-regions of images.
> The need arises from having very large images which are highly compressed
> (usually JPEG or JBIG2). The current implementation decodes the entire image
> into memory at full resolution, even if rendering is done at a much lower
> resolution.
> Since the change required augmenting the way Filters work (to allow
> partial/subsampled decoding), it also includes a partial fix for PDFBOX-3340.
>
>
> This change introduces "DecodeOptions" which are currently only applicable
> for images. They include requesting only metadata (for PDImageXObject's
> repair method), subsampling and sub-region (similar to
> javax.imagio.ImageReadParam).
> Since not all filters can or do honor (use) the options, the DecodeOptions
> class contains a flag. Filters that honor the options (subsample / decode
> only requested region) set it to true. If the flag is false, the subsampling
> or cropping should be done after decoding, to ensure consistency.
> PageDrawer was modified so it uses subsampling based on the ratio of the
> desired output to the original image.
>
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
