[OpenJDK 2D-Dev] Integrated: 8256264: Printed GlyphVector outline with low DPI has bad quality on Windows

[Alexander Scherbatiy]

On Thu, 12 Nov 2020 10:32:16 GMT, Alexander Scherbatiy <alexsch at openjdk.org> wrote:

> Printing text using GlyphVector outline has bad quality on printers with low DPI on Windows.
> The GDI system used for text printing on Windows accepts only integer path coordinates.
> Rounding GlyphVector outline coordinates leads to distorted printed text.
> 
> To reproduce the issue run the [PrintGlyphVectorOutlineSample](https://bugs.openjdk.java.net/secure/attachment/91398/PrintGlyphVectorOutlineSample.java)  file on Windows and select a low DPI
> printer in the printer dialog. The sample prints two lines, one using Graphics drawString() method and another by
> filling GlyphVector outline. Chars on the second line are distorted.
> 
> It is also possible to reproduce the issue running the sample and printing the text to PDF: [fill-glyph-vector-outline.png](https://bugs.openjdk.java.net/secure/attachment/91397/fill-glyph-vector-outline.png)
> 
> The proposed fix introduce "sun.java2d.print.enablePathPrecisionScale" property which being enabled
> scales the GDI WorldTransform down and GlyphVector outline coordinates up.
> This allows to keep some digits after a dot from being rounded.
> The value for scaling is chosen to be 1000 in the same way how it is used  by `String trunc(float f)` method from PSPrinterJob class on Linux:
> https://github.com/openjdk/jdk/blob/ed615e3ca0d681e8e67cdbf1d5d964979ccd7888/src/java.desktop/share/classes/sun/print/PSPrinterJob.java#L1489
> 
> See the  [fill-glyph-vector-outline-enable-path-scale-factor.png](https://bugs.openjdk.java.net/secure/attachment/91399/fill-glyph-vector-outline-enable-path-scale-factor.png) screenshot which shows how the GlyphVector outline is filled after the fix with the enabled "sun.java2d.print.enablePathPrecisionScale" option.
> 
> [fill-glyph-vector-outline-diff.png](https://bugs.openjdk.java.net/secure/attachment/91400/fill-glyph-vector-outline-diff.png) shows difference of GlyphVector outline printing before and after the fix.

This pull request has now been integrated.

Changeset: d6dd440c
Author:    Alexander Scherbatiy <alexsch at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/d6dd440c
Stats:     470 lines in 4 files changed: 459 ins; 0 del; 11 mod

8256264: Printed GlyphVector outline with low DPI has bad quality on Windows

Reviewed-by: serb

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PR: https://git.openjdk.java.net/jdk/pull/1183