Do image comparison with fuzz

Looks like native png and jpeg libs on some devices have rounding
problems, so compare the color values with a fuzz of 3. This fixes
this test on Maemo 5 and 6.

Reviewed-by: Benjamin Poulain

1 files changed, 18 insertions, 1 deletions

diff --git a/tests/auto/qimagereader/tst_qimagereader.cpp b/tests/auto/qimagereader/tst_qimagereader.cpp
index fe2a719..e9ef070 100644
--- a/tests/auto/qimagereader/tst_qimagereader.cpp
+++ b/tests/auto/qimagereader/tst_qimagereader.cpp
@@ -315,7 +315,24 @@ void tst_QImageReader::jpegRgbCmyk()
     QImage image1(prefix + QLatin1String("YCbCr_cmyk.jpg"));
     QImage image2(prefix + QLatin1String("YCbCr_cmyk.png"));
 
-    QCOMPARE(image1, image2);
+    // first, do some obvious tests
+    QCOMPARE(image1.height(), image2.height());
+    QCOMPARE(image1.width(), image2.width());
+    QCOMPARE(image1.format(), image2.format());
+    QCOMPARE(image1.format(), QImage::Format_RGB32);
+
+    // compare all the pixels with a slack of 3. This ignores rounding errors in libjpeg/libpng
+    for (int h = 0; h < image1.height(); ++h) {
+        const uchar *s1 = image1.constScanLine(h);
+        const uchar *s2 = image2.constScanLine(h);
+        for (int w = 0; w < image1.width() * 4; ++w) {
+            if (*s1 != *s2) {
+                QVERIFY2(qAbs(*s1 - *s2) <= 3, qPrintable(QString("images differ in line %1, col %2 (image1: %3, image2: %4)").arg(h).arg(w).arg(*s1, 0, 16).arg(*s2, 0, 16)));
+            }
+            s1++;
+            s2++;
+        }
+    }
 }
 
 void tst_QImageReader::setScaledSize_data()