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Posted to dev@pdfbox.apache.org by "Tilman Hausherr (JIRA)" <ji...@apache.org> on 2018/03/02 17:02:00 UTC
[jira] [Comment Edited] (PDFBOX-4137) Allow subsampled/downscaled
rendering of images, and rendering subimages
[ https://issues.apache.org/jira/browse/PDFBOX-4137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16383815#comment-16383815 ]
Tilman Hausherr edited comment on PDFBOX-4137 at 3/2/18 5:01 PM:
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Yeah on my new machine, with energy settings set to maximum performance, existing code does it in 1200 ms (best of several tries), new code in 900 ms.
Btw my code wouldn't have been possible without yours. I have looked at the problem just 2 weeks ago and didn't come up with a solution. Only by looking through your code I understood that it is all about bypassing the filters.
was (Author: tilman):
Yeah on my new machine, with energy settings set to maximum performance, existing code does it in 1200 MS (best of several tries), new code in 900 ms.
Btw my code wouldn't have been possible without yours. I have looked at the problem just 2 weeks ago and didn't come up with a solution. Only by looking through your code I understood that it is all about bypassing the filters.
> 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, 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.
>
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