RFR: 8326027: Comparing buffered images of white background frame fails in Mac

[Alexey Ivanov]

On Thu, 29 Aug 2024 04:38:29 GMT, Tejesh R <tr at openjdk.org> wrote:

> On analysis of captured image, it is observed that there are few pixels which vary slightly w.r.t to expected color. Hence tolerance is included in color comparison. 
> Tested in mach5 multiple time and its green.

I wonder whether the tolerance wouldn't be required if `Robot.createMultiResolutionScreenCapture` was used to create the screenshot and then analysing the original image which didn't go through down-scaling in High DPI environment.

test/jdk/javax/swing/JFrame/JFrameBackgroundRefreshTest.java line 140:

> 138: 
> 139:     private static boolean compareImages(BufferedImage bufferedImage) {
> 140:         Color firstPixel = new Color(bufferedImage.getRGB(0,0));

Suggestion:

        final Color firstPixel = new Color(bufferedImage.getRGB(0, 0));

test/jdk/javax/swing/JFrame/JFrameBackgroundRefreshTest.java line 151:

> 149:     }
> 150: 
> 151:     private static boolean compareColor(Color c1, Color c2) {

Shall we move such a method into `Util`?

More and more test cases add tolerance to color comparison. Yeah, it's simple enough… and adding a library makes it somewhat harder to run a test in stand-alone mode, without jtreg.

test/jdk/javax/swing/JFrame/JFrameBackgroundRefreshTest.java line 155:

> 153:                 Math.abs(c1.getGreen() - c2.getGreen()) < TOLERANCE &&
> 154:                 Math.abs(c1.getBlue() - c2.getBlue()) < TOLERANCE;
> 155:     }

Suggestion:

    private static boolean compareColor(Color c1, Color c2) {
        return Math.abs(c1.getRed() - c2.getRed()) < TOLERANCE
                && Math.abs(c1.getGreen() - c2.getGreen()) < TOLERANCE
                && Math.abs(c1.getBlue() - c2.getBlue()) < TOLERANCE;
    }

Java Coding Style recommends putting operators on the continuation line, it makes it obvious to the reader it is a continuation of an expression.

-------------

PR Review: https://git.openjdk.org/jdk/pull/20760#pullrequestreview-2268640859
PR Review Comment: https://git.openjdk.org/jdk/pull/20760#discussion_r1736144750
PR Review Comment: https://git.openjdk.org/jdk/pull/20760#discussion_r1736154776
PR Review Comment: https://git.openjdk.org/jdk/pull/20760#discussion_r1736145854