On Fri, 28 Aug 2026 18:15:32 GMT, Martin Fox <[email protected]> wrote:
> This PR attempts to improve LCD text rendering on Windows and Linux. Changes > include: > > - (Windows only) When setting up DirectWrite the code now uses the > NATURAL_SYMMETRIC rendering mode except for very small glyphs where it uses > NATURAL. Using NATURAL_SYMMETRIC avoids distorted glyphs at specific pixel > sizes (see [JDK-8389632](https://bugs.openjdk.org/browse/JDK-8389632)) and > retains the curves along the top and bottom of the glyphs. Using NATURAL at > small sizes avoids glyphs turning very fuzzy and light. > > - The code is now consistently converts the colors from sRGB to a linear > space (more or less), composites them, and then converts the result back to > sRGB. > > - The shader applies a contrast equation to the LCD glyph mask which helps > emphasize the stems. The same equation is used by Skia and probably added by > Microsoft when they cleaned up text rendering for Chromium. BTW it’s just the > equation for a parabola that goes through points (0, 0) and (1, 1). > > My testing was mostly done on a 27 inch display with a resolution of > 2560x1440 and a screen scale of 150%. This was low enough to notice a > difference. Resolutions higher than that (like full-on Retina) tend to hide a > lot of sins. > > I recommend reading “The Raster Tragedy in Skia” which is concise but covers > a lot of ground. It contains a section on the challenges of compositing text > in sRGB space and also the issues getting LCD text to look dark enough > without inflating the stems. I wish I had found this earlier in the process. > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai). Interestingly, I don't see much difference on my windows 11 (but it could be just me, or the result might also depend on the local user preferences). example this pr: <img width="1430" height="1003" alt="Screenshot 2026-08-28 153520" src="https://github.com/user-attachments/assets/0bb70016-58e7-4378-81ec-d2b36ef32192"; /> master: <img width="1430" height="1003" alt="Screenshot 2026-08-28 154445" src="https://github.com/user-attachments/assets/37104942-0b5d-4cbc-9854-6b5aed38ee2c"; /> diff: <img width="1317" height="1039" alt="Screenshot 2026-08-28 154949" src="https://github.com/user-attachments/assets/cdc5143a-41b2-447a-82ff-11af6e5fd059"; /> another case: this pr: <img width="1430" height="1003" alt="Screenshot 2026-08-28 153422" src="https://github.com/user-attachments/assets/760a47a0-6fbc-446c-abbf-425784db6529"; /> master: <img width="1430" height="1003" alt="Screenshot 2026-08-28 154503" src="https://github.com/user-attachments/assets/c6e6fea5-1dd8-4350-bb1e-ee8ddcfaea40"; /> the screenshots above were made on a standard dell laptop 1920x1080 100% scale. modules/javafx.graphics/src/main/java/com/sun/javafx/font/directwrite/DWGlyph.java line 272: > 270: int measuringMode = OS.DWRITE_MEASURING_MODE_NATURAL; > 271: DWRITE_MATRIX matrix = strike.matrix; /* can be null */ > 272: if (matrix != null && !DWFontStrike.SUBPIXEL_Y) { minor suggestion: extract this logic into an appropriately named method to 1) avoid double assignment 2) make the code self-explanatory move the new comment to that method as well. modules/javafx.graphics/src/main/java/com/sun/prism/impl/ps/BaseShaderGraphics.java line 2101: > 2099: initLCDSampleRT(); > 2100: } > 2101: // To convert sRGB to (approximately) linear the gamma we > use is please update the copyright year modules/javafx.graphics/src/main/java/com/sun/prism/impl/ps/BaseShaderGraphics.java line 2104: > 2102: // 2.233333 which more closely approximates the real sRGB > 2103: // function compared to the usual value of 2.2. > 2104: float gamma = 2.233333f; 1) `PrismFontFactory.getLCDContrast()` contains platform-specific code (isWindows) and used in multiple places (also in `SWGraphics`). would it make more sense to move this change there? 2) should a similar change be applied to SWGraphics:668 ? ------------- PR Comment: https://git.openjdk.org/jfx/pull/2284#issuecomment-5458586200 PR Comment: https://git.openjdk.org/jfx/pull/2284#issuecomment-5458590706 PR Comment: https://git.openjdk.org/jfx/pull/2284#issuecomment-5458600518 PR Review Comment: https://git.openjdk.org/jfx/pull/2284#discussion_r3884303003 PR Review Comment: https://git.openjdk.org/jfx/pull/2284#discussion_r3884312714 PR Review Comment: https://git.openjdk.org/jfx/pull/2284#discussion_r3884335062
