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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 commented on PDFBOX-4205:
---------------------------------------------
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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