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https://issues.apache.org/jira/browse/PDFBOX-4205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17050006#comment-17050006
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Constantine Dokolas edited comment on PDFBOX-4205 at 3/3/20 8:44 AM:
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JIRA decided to cancel the changes to my comment when switching from "Visual"
mode to "Text" mode and I lost all my precious elucidations. :P This is a
summary:
The test should be done only by loading a grayscale image, which correctly
creates the linear grayscale colorspace; not via pseudo-conversion, which uses
sRGB colorspace throughout. The problem will be how to determine what the
"reference" data are. The objective is that the byte values should be preserved
all the way to the XObject stream.
It may still be that the specific test shows some bug appearing. I will check
later. It may be that the colorspace should be also considered...
was (Author: cdokolas):
JIRA decided to cancel the changes to my comment when switching from "Visual"
mode to "Text" mode and I lost all my precious elucidations. :P This is a
summary:
The test should be done only by loading a grayscale image, which correctly
creates the linear grayscale colorspace; not via pseudo-conversion, which uses
sRGB colorspace throughout.
It may still be that the specific test shows some bug appearing. I will check
later. It may be that the colorspace should be also considered...
> LosslessFactory alters image
> ----------------------------
>
> Key: PDFBOX-4205
> URL: https://issues.apache.org/jira/browse/PDFBOX-4205
> Project: PDFBox
> Issue Type: Bug
> Affects Versions: 2.0.7, 2.0.8, 2.0.9
> Environment: Ubuntu 16.04
> Reporter: Harry Dent
> Priority: Minor
> Attachments: image-2020-02-24-17-59-08-300.png, lossy.png,
> picture_of_text.png
>
>
> The attached grayscale png becomes lighter when run through the following
> code snippet:
> {code:java}
> BufferedImage image = ImageIO.read(new File("picture_of_text.png"));
> PDImageXObject xObject = LosslessFactory.createFromImage(new PDDocument(),
> image);
> BufferedImage lossy = xObject.getImage();
> ImageIO.write(lossy, "png", new File("lossy.png"));
> {code}
> The difference is easiest to spot by looking at the "S" in "41st". The loss
> in quality occurs in {{createFromImage()}} (rather than {{getImage()}}),
> which can be shown by embedding the {{PDImageXObject}} into a {{PDDocument}}
> and then saving this document to a file.
>
>
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