Add support for tiled, color indexed tiff files

For color index images, the tiff handler uses scanline based
reading. The tiff decoder does not support that if the image is stored
in tiled format. This commit adds tile based reading for such cases.

[ChangeLog][TIFF] Added support for tiled, color indexed tiff files

Task-number: QTBUG-12636
Change-Id: Ic759903c75c8252267429f01e3dd9706fc516f8f
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/plugins/imageformats/tiff/qtiffhandler.cpp

@@ -385,11 +385,38 @@ bool QTiffHandler::read(QImage *image)
                 }
 
                 image->setColorTable(qtColorTable);
-                for (uint32 y=0; y<height; ++y) {
-                    if (TIFFReadScanline(tiff, image->scanLine(y), y, 0) < 0) {
+
+                if (TIFFIsTiled(tiff)) {
+                    quint32 tileWidth, tileLength;
+                    TIFFGetField(tiff, TIFFTAG_TILEWIDTH, &tileWidth);
+                    TIFFGetField(tiff, TIFFTAG_TILELENGTH, &tileLength);
+                    uchar *buf = (uchar *)_TIFFmalloc(TIFFTileSize(tiff));
+                    if (!tileWidth || !tileLength || !buf) {
+                        _TIFFfree(buf);
                         d->close();
                         return false;
                     }
+                    for (quint32 y = 0; y < height; y += tileLength) {
+                        for (quint32 x = 0; x < width; x += tileWidth) {
+                            if (TIFFReadTile(tiff, buf, x, y, 0, 0) < 0) {
+                                _TIFFfree(buf);
+                                d->close();
+                                return false;
+                            }
+                            quint32 linesToCopy = qMin(tileLength, height - y);
+                            quint32 widthToCopy = qMin(tileWidth, width - x);
+                            for (quint32 i = 0; i < linesToCopy; i++)
+                                ::memcpy(image->scanLine(y + i) + x, buf + (i * tileWidth), widthToCopy);
+                        }
+                    }
+                    _TIFFfree(buf);
+                } else {
+                    for (uint32 y=0; y<height; ++y) {
+                        if (TIFFReadScanline(tiff, image->scanLine(y), y, 0) < 0) {
+                            d->close();
+                            return false;
+                        }
+                    }
                 }
 
                 // free redTable, greenTable and greenTable done by libtiff

tests/auto/tiff/tst_qtiff.cpp

@@ -81,6 +81,9 @@ private slots:
     void multipage_data();
     void multipage();
 
+    void tiled_data();
+    void tiled();
+
 private:
     QString prefix;
 };
@@ -153,6 +156,8 @@ void tst_qtiff::readImage_data()
     QTest::newRow("rgb_orientation_7") << QString("rgb_orientation_7.tiff") << QSize(64, 64);
     QTest::newRow("rgb_orientation_8") << QString("rgb_orientation_8.tiff") << QSize(64, 64);
     QTest::newRow("teapot") << QString("teapot.tiff") << QSize(256, 256);
+    QTest::newRow("indexed_nontiled") << QString("indexed_nontiled.tif") << QSize(512, 384);
+    QTest::newRow("indexed_tiled") << QString("indexed_tiled.tif") << QSize(512, 384);
 }
 
 void tst_qtiff::readImage()
@@ -557,5 +562,22 @@ void tst_qtiff::multipage()
     QCOMPARE(reader.jumpToNextImage(), false);
 }
 
+void tst_qtiff::tiled_data()
+{
+    QTest::addColumn<QString>("expectedFile");
+    QTest::addColumn<QString>("tiledFile");
+    QTest::newRow("Indexed") << "indexed_nontiled.tif" << "indexed_tiled.tif";
+}
+
+void tst_qtiff::tiled()
+{
+    QFETCH(QString, expectedFile);
+    QFETCH(QString, tiledFile);
+
+    QImage expectedImage(prefix + expectedFile);
+    QImage tiledImage(prefix + tiledFile);
+    QCOMPARE(expectedImage, tiledImage);
+}
+
 QTEST_MAIN(tst_qtiff)
 #include "tst_qtiff.moc"

tests/shared/images/tiff.qrc

@@ -41,5 +41,7 @@
         <file>tiff/rgb_orientation_8.tiff</file>
         <file>tiff/teapot.tiff</file>
         <file>tiff/colorful.bmp</file>
+        <file>tiff/indexed_tiled.tif</file>
+        <file>tiff/indexed_nontiled.tif</file>
     </qresource>
 </RCC>