[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 2wxsy5823...@opayq.com changed: What|Removed |Added See Also||https://bugs.kde.org/show_b ||ug.cgi?id=424817 -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #23 from Tobias Deiminger --- (In reply to Tobias Deiminger from comment #22) > $ compare -metric SSIM test-1-original.jpg test-1-cairo-200dpi.png null: 2>&1 > 0.826331 There was a mistake in the example. The compare tool needs two identical sized images (it works otherwise, but does a completely different thing then). So now I scale up poppler output back to original size with a high quality filter before comparing images. Here are some first test results: | Test conditions| avg. SSIM (higher is better) | orig_size new_size scale SplashCairo Lanczos(*) 1894x2798 1799x2658 0.95 0.894696 0.97901 0.986598 1894x2798 1704x2518 0.90 0.940628 0.975257 0.961978 1894x2798 1609x2378 0.85 0.939805 0.972347 0.961621 1894x2798 1515x2238 0.80 0.896754 0.965689 0.972571 1894x2798 1420x2098 0.75 0.944005 0.955174 0.969092 1894x2798 1325x1958 0.70 0.944173 0.954734 0.966077 1894x2798 1231x1818 0.65 0.913747 0.959678 0.963164 1894x2798 1136x1678 0.60 0.932564 0.939862 0.959964 1894x2798 1041x1538 0.55 0.945498 0.926968 0.948855 1894x2798 947x1399 0.50 0.888512 0.951904 0.952485 1894x2798 852x1259 0.45 0.893747 0.944982 0.942065 1894x2798 757x1119 0.40 0.926194 0.938078 0.936967 1894x2798 6620x979 0.35 0.908621 0.928839 0.929847 1894x2798 568x 839 0.30 0.871821 0.91770.9235 1894x2798 473x 699 0.25 0.909859 0.903451 0.909088 1894x2798 378x 559 0.20 0.894681 0.88581 0.894793 1894x2798 284x 419 0.15 0.869878 0.879541 0.876719 1894x2798 189x 279 0.10 0.861054 0.858674 0.863767 If there were no further mistakes, that was a quite significant win for Cairo over Splash. I'm planning to publish my test methods and open an issue at poppler. There we can discuss if we take action. (*) Lanczos downsampling (with IM7) is included for reference and plausibility. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #22 from Tobias Deiminger --- Found a quite on-topic paper [0], where it's suggested to compute local indexes for luminance comparison, contrast comparison and structural comparison to assess the quality of downsampling algorithm. If I understand correctly, structural comparison refers to SSIM [1] which can be calculated using latest ImageMagick 7. For example: $ compare -metric SSIM test-1-original.jpg test-1-cairo-200dpi.png null: 2>&1 0.826331 $ compare -metric SSIM test-1-original.jpg test-1-splash-200dpi.png null: 2>&1 0.824194 Higher is better, so cairo slightly wins in that structural comparison example. For the test, test-1-cairo-200dpi.png and test-1-splash-200dpi.png have been generated locally from test-1.pdf using poppler_page_render and renderToImage respectively in a standalone application. If no one disagrees (in the sense that observations wouldn't be meaningful enough or lack too much context), I'm going to follow this track and do broader tests with more metrics and try to gain better understand of the results. [0] Korneta, 2017 [1] https://en.wikipedia.org/wiki/Structural_similarity -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #21 from David Hurka --- (In reply to Tobias Deiminger from comment #20) > But that impression is subjective, can we try to > quantize a bit what "better" means? E.g., we could measure "densitiy of > black" in a histogram, right? Any other hints what "better" could mean here? My first idea is to agree to using a histogram, and make an artifical reference “scan”, containing various edges at various sizes, angles, sharpnesses, resolutions,... and make a histogram to count how many pixels in the rendering output are used for edges. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #20 from Tobias Deiminger --- (In reply to yousifjkadom from comment #14) > Created attachment 120583 [details] > test-1b-okular Can you tell us the resolution of your display, and the Okular zoom level at which you observe bad behavior? From screenshots I'd say it's 1366x768 display resolution, correct? But can't tell zoom level because of "fit width" setting. I'm asking because poppler switches between two image scaling algorithm, depending on whether upscaling or downscaling is needed. The embedded image in test-1.pdf has 300dpi. If you watch it on a 100dpi display at 100% zoom, it's actually scaled down (with bresenham in Okular/Splash, nearest neighbor in Evince/Cairo). If you do the same on a HiDPI display, the image is probably scaled up (bilinear interpolation in both Okular and Evince). Scaling algorithm is the most obvious difference between Evince/xreader and Okular. But you say you see same bad rendering with text documents. That puzzles me, glyph rendering takes quite different paths. I'd agree that screenshot test-1b-xreader.png looks slightly better than test-1b-okular.png. But that impression is subjective, can we try to quantize a bit what "better" means? E.g., we could measure "densitiy of black" in a histogram, right? Any other hints what "better" could mean here? -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #19 from Albert Astals Cid --- By the way, i guess this is due to cultural barriers/translation issues, but your tone is way out of line. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 Albert Astals Cid changed: What|Removed |Added Status|NEEDSINFO |REPORTED Resolution|WAITINGFORINFO |--- --- Comment #18 from Albert Astals Cid --- user attached some screenshots -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #17 from yousifjka...@yahoo.com --- Created attachment 120586 --> https://bugs.kde.org/attachment.cgi?id=120586=edit test-2-xreader -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #16 from yousifjka...@yahoo.com --- Created attachment 120585 --> https://bugs.kde.org/attachment.cgi?id=120585=edit test-2-okular -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #15 from yousifjka...@yahoo.com --- Created attachment 120584 --> https://bugs.kde.org/attachment.cgi?id=120584=edit test-1b-xreader -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #14 from yousifjka...@yahoo.com --- Created attachment 120583 --> https://bugs.kde.org/attachment.cgi?id=120583=edit test-1b-okular -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #13 from yousifjka...@yahoo.com --- Created attachment 120582 --> https://bugs.kde.org/attachment.cgi?id=120582=edit test-1a-xreader -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #12 from yousifjka...@yahoo.com --- Created attachment 120581 --> https://bugs.kde.org/attachment.cgi?id=120581=edit test-1a-okular -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #11 from yousifjka...@yahoo.com --- Take screenshots that you asked me for. I have to add that NOT ONLY SCANNED PDF affected by this ! Even formatted PDF (text based PDF) also affected when black tone is lower in Okular & characters less sharp ... -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #10 from David Hurka --- Created attachment 120580 --> https://bugs.kde.org/attachment.cgi?id=120580=edit Pixels Using Albert’s screenshot, one could say that Evince and Okular draw slightly different. Indeed, where the arrow points, Evince is sharper than Okular, resulting in a higher contrast and a differently perceived black tone. Could have these reasons: a) Both have a slightly different alignment of the scanned image, resulting in different sampling of rendered pixels which are not exactly on image pixels. b) Both have same alignment, but use different filtering. (Bilinear, Bicubic, Nearest Neighbour,... In fact, Okular does not use nearest neighbour, causing smeared edges on scans. Maybe Evince does?) c) this happened just at random for exactly these zoom factors. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 Tobias Deiminger changed: What|Removed |Added CC||haxti...@posteo.de --- Comment #9 from Tobias Deiminger --- Created attachment 120522 --> https://bugs.kde.org/attachment.cgi?id=120522=edit side by side comparison of test-1 rendered with Evince (l) and Okular (r) (In reply to yousifjkadom from comment #6) > If you concentrate well, you will noticed that black tone (DENSITY OF BLACK) > is lower in Okular than Evence. So, picture in Okular less in dexterity than > Evince. I'm with Albert, the scans look equally bad in both Evince and Okular (see attachment). Regarding black tone, I measured RGB values with KColorChooser and they are just the same. Can you show how it looks different at your side? I mean don't just attach the PDF, but a screenshot showing it in Evince next to Okular. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #8 from yousifjka...@yahoo.com --- Created attachment 120519 --> https://bugs.kde.org/attachment.cgi?id=120519=edit test-2 -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #7 from yousifjka...@yahoo.com --- Created attachment 120518 --> https://bugs.kde.org/attachment.cgi?id=120518=edit test-1 -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #6 from yousifjka...@yahoo.com --- Hi.Sorry for delay in response, it was at night in my country & I went to sleep just after posting this bug. Dear, I attach 2 PDF files, each composed from single page. In each page (each PDF file) there are: - pictures - Arabic characters - English characters If you can not evaluate Arabic, then please look carefully for both pictures & English paragraphs. Please concentrate on BLACK TONE. If you concentrate well, you will noticed that black tone (DENSITY OF BLACK) is lower in Okular than Evence. So, picture in Okular less in dexterity than Evince. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 Albert Astals Cid changed: What|Removed |Added Resolution|--- |WAITINGFORINFO Status|REPORTED|NEEDSINFO --- Comment #5 from Albert Astals Cid --- I don't know how to read arabic so it's kind of hard to me to say but looking at https://i.imgur.com/QvLAH99.png evince and okular look as terrible to me. Please attach a screenshot showing the problem. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 Albert Astals Cid changed: What|Removed |Added CC||aa...@kde.org --- Comment #4 from Albert Astals Cid --- (In reply to David Hurka from comment #3) > However, how does it look different in Evince? It uses the same rendering > backend It does not use the same rendering backend. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #3 from David Hurka --- Created attachment 120507 --> https://bugs.kde.org/attachment.cgi?id=120507=edit Page 188 in Okular A friend just told me that this is readable. However, how does it look different in Evince? It uses the same rendering backend, so theoretically it should look the same. -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #2 from yousifjka...@yahoo.com --- Please take care for this issue because it is very important for those users that live in 3rd world countries where most of PDF books are scanned not formatted -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 --- Comment #1 from yousifjka...@yahoo.com --- Created attachment 120506 --> https://bugs.kde.org/attachment.cgi?id=120506=edit scanned-pdf -- You are receiving this mail because: You are watching all bug changes.
[okular] [Bug 408222] Okular is bad in displaying of scanned PDF ! Please fix this !
https://bugs.kde.org/show_bug.cgi?id=408222 yousifjka...@yahoo.com changed: What|Removed |Added Summary|Okular is bad in|Okular is bad in displaying |visualization of scanned|of scanned PDF ! Please fix |PDF ! Please fix this ! |this ! -- You are receiving this mail because: You are watching all bug changes.
