Add support for reading BigTIFF

All recent versions of libtiff has support for the 64bit-indexed
BigTIFF format. Allow reading it by recognizing its magic number.

[ChangeLog][TIFF] Add support for reading BigTIFF

Fixes: QTBUG-80538
Change-Id: I7fcb72d77e4a0bdcb38ab96e9f6cfaff7cf4ad49
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/plugins/imageformats/tiff/qtiffhandler.cpp

@@ -205,9 +205,14 @@ bool QTiffHandlerPrivate::canRead(QIODevice *device)
 
     // current implementation uses TIFFClientOpen which needs to be
     // able to seek, so sequential devices are not supported
-    QByteArray header = device->peek(4);
-    return header == QByteArray::fromRawData("\x49\x49\x2A\x00", 4)
-           || header == QByteArray::fromRawData("\x4D\x4D\x00\x2A", 4);
+    char h[4];
+    if (device->peek(h, 4) != 4)
+        return false;
+    if ((h[0] == 0x49 && h[1] == 0x49) && (h[2] == 0x2a || h[2] == 0x2b) && h[3] == 0)
+        return true; // Little endian, classic or bigtiff
+    if ((h[0] == 0x4d && h[1] == 0x4d) && h[2] == 0 && (h[3] == 0x2a || h[3] == 0x2b))
+        return true; // Big endian, classic or bigtiff
+    return false;
 }
 
 bool QTiffHandlerPrivate::openForRead(QIODevice *device)

tests/auto/tiff/tst_qtiff.cpp

@@ -90,6 +90,9 @@ private slots:
     void colorSpace_data();
     void colorSpace();
 
+    void bigtiff_data();
+    void bigtiff();
+
 private:
     QString prefix;
 };
@@ -173,6 +176,10 @@ void tst_qtiff::readImage_data()
     QTest::newRow("tiled_oddsize_mono") << QString("tiled_oddsize_mono.tiff") << QSize(59, 71);
     QTest::newRow("16bpc") << QString("16bpc.tiff") << QSize(64, 46);
     QTest::newRow("gray16") << QString("gray16.tiff") << QSize(64, 46);
+    QTest::newRow("big_rgb") << QString("big_rgb.tiff") << QSize(64, 64);
+    QTest::newRow("big_rgb_bigendian") << QString("big_rgb_bigendian.tiff") << QSize(64, 64);
+    QTest::newRow("big_grayscale") << QString("big_grayscale.tiff") << QSize(64, 64);
+    QTest::newRow("big_16bpc") << QString("big_16bpc.tiff") << QSize(64, 46);
 }
 
 void tst_qtiff::readImage()
@@ -665,5 +672,27 @@ void tst_qtiff::colorSpace()
     QCOMPARE(image2, image);
 }
 
+void tst_qtiff::bigtiff_data()
+{
+    QTest::addColumn<QString>("expectedFile");
+    QTest::addColumn<QString>("bigtiffFile");
+
+    QTest::newRow("big_rgb") << QString("original_rgb.tiff") << QString("big_rgb.tiff");
+    QTest::newRow("big_rgb_bigendian") << QString("original_rgb.tiff") << QString("big_rgb_bigendian.tiff");
+    QTest::newRow("big_grayscale") << QString("original_grayscale.tiff") << QString("big_grayscale.tiff");
+    QTest::newRow("big_16bpc") << QString("16bpc.tiff") << QString("big_16bpc.tiff");
+}
+
+void tst_qtiff::bigtiff()
+{
+    QFETCH(QString, expectedFile);
+    QFETCH(QString, bigtiffFile);
+
+    QImage expectedImage(prefix + expectedFile);
+    QImage bigtiffImage(prefix + bigtiffFile);
+    QVERIFY(!bigtiffImage.isNull());
+    QCOMPARE(expectedImage, bigtiffImage);
+}
+
 QTEST_MAIN(tst_qtiff)
 #include "tst_qtiff.moc"

tests/shared/images/tiff.qrc

@@ -52,5 +52,9 @@
         <file>tiff/oddsize_mono.tiff</file>
         <file>tiff/tiled_rgb.tiff</file>
         <file>tiff/gray16.tiff</file>
+        <file>tiff/big_rgb.tiff</file>
+        <file>tiff/big_16bpc.tiff</file>
+        <file>tiff/big_grayscale.tiff</file>
+        <file>tiff/big_rgb_bigendian.tiff</file>
     </qresource>
 </RCC>