Wrong colors of Images with semitransparency rendered to PDF using CGPDFContext or [NSView dataWithPDFInsideRect:]
Originator: | hannes.oud.dev | ||
Number: | rdar://46897333 | Date Originated: | 21-Dec-2018 12:16 PM |
Status: | Closed | Resolved: | DUPLICATE OF 46671538 |
Product: | macOS + SDK | Product Version: | Xcode 10.1 (10B61) |
Classification: | Other Bug | Reproducible: | Always |
Summary: When drawing an image with semitransparent pixels in a PDF context the color blending is wrong/unexpected, leading to too dark or desaturated colors. Opaque and fully transparent pixels are handled correctly. Steps to Reproduce: Open attached playground Run playground. Scroll to the bottom and compare the images „expectedResult“ to „pdfResult1“ or „pdfResult2“ Expected Results: pdfResult1 and pdfResult2 should look like expectedResult Actual Results: The blended colors in second and third column of each grid look too dark and grey Version: Xcode 10.1 (10B61) Notes: One theory about this is that premultiplied alpha is somehow not respected in the blending process. Also please play around with the variable backgroundColor in the playground. If you set it to red, the top row of each grid should render completely red, as the grids top row colors are plain red with varying alpha. I think the same applies to CoreGraphics of iOS 12 SDK.
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Closed as duplicate
DUPLICATE OF 46671538