Merge pull request OSGeo#12547 from rouault/FLIR_PNG_16bit

JPEG: read FLIR thermal image stored as 16-bit PNG with little-endian byte order

Author: rouault

autotest/gdrivers/data/jpeg/flir/FLIR_16bit.jpg

@@ -1341,6 +1341,17 @@ def test_jpeg_flir_png():
     assert ds.GetRasterBand(1).Checksum() == 761
 
 
+###############################################################################
+# Open JPEG image with FLIR metadata and raw thermal image as PNG 16 bit
+
+
+def test_jpeg_flir_png_16_bit():
+
+    ds = gdal.Open('JPEG:"data/jpeg/flir/FLIR_16bit.jpg":FLIR_RAW_THERMAL_IMAGE')
+    assert ds.GetRasterBand(1).DataType == gdal.GDT_UInt16
+    assert ds.GetRasterBand(1).ComputeRasterMinMax(False) == (65280, 65280)
+
+
 ###############################################################################
 # Open JPEG image with FLIR metadata and raw thermal image as raw
 

autotest/gdrivers/jpeg.py

@@ -2905,7 +2905,14 @@ GDALDataset *JPGDatasetCommon::OpenFLIRRawThermalImage()
     if (m_abyRawThermalImage.size() > 4 &&
         memcmp(m_abyRawThermalImage.data(), "\x89PNG", 4) == 0)
     {
-        auto poRawDS = GDALDataset::Open(osTmpFilename.c_str());
+        // FLIR 16-bit PNG have a wrong endianness.
+        // Cf https://exiftool.org/TagNames/FLIR.html: "Note that most FLIR
+        // cameras using the PNG format seem to write the 16-bit raw image data
+        // in the wrong byte order."
+        const char *const apszPNGOpenOptions[] = {
+            "@BYTE_ORDER_LITTLE_ENDIAN=YES", nullptr};
+        auto poRawDS = GDALDataset::Open(osTmpFilename.c_str(), GDAL_OF_RASTER,
+                                         nullptr, apszPNGOpenOptions, nullptr);
         if (poRawDS == nullptr)
         {
             CPLError(CE_Failure, CPLE_AppDefined, "Invalid raw thermal image");

frmts/jpeg/jpgdataset.cpp

@@ -1402,8 +1402,13 @@ CPLErr PNGDataset::LoadInterlacedChunk(int iLine)
     bool bRet = safe_png_read_image(hPNG, png_rows, sSetJmpContext);
 
     // Do swap on LSB machines. 16-bit PNG data is stored in MSB format.
+    if (bRet && nBitDepth == 16
 #ifdef CPL_LSB
-    if (bRet && nBitDepth == 16)
+        && !m_bByteOrderIsLittleEndian
+#else
+        && m_bByteOrderIsLittleEndian
+#endif
+    )
     {
         for (int i = 0; i < GetRasterYSize(); i++)
         {
@@ -1414,7 +1419,6 @@ CPLErr PNGDataset::LoadInterlacedChunk(int iLine)
             }
         }
     }
-#endif
 
     CPLFree(png_rows);
     CPLFree(dummy_row);
@@ -1492,10 +1496,16 @@ CPLErr PNGDataset::LoadScanline(int nLine)
     nBufferLines = 1;
 
     // Do swap on LSB machines. 16-bit PNG data is stored in MSB format.
+    if (nBitDepth == 16
 #ifdef CPL_LSB
-    if (nBitDepth == 16)
-        GDALSwapWords(row, 2, GetRasterXSize() * GetRasterCount(), 2);
+        && !m_bByteOrderIsLittleEndian
+#else
+        && m_bByteOrderIsLittleEndian
 #endif
+    )
+    {
+        GDALSwapWords(row, 2, GetRasterXSize() * GetRasterCount(), 2);
+    }
 
     return CE_None;
 }
@@ -1973,6 +1983,10 @@ GDALDataset *PNGDataset::OpenStage2(GDALOpenInfo *poOpenInfo, PNGDataset *&poDS)
     // Open overviews.
     poDS->oOvManager.Initialize(poDS, poOpenInfo);
 
+    // Used by JPEG FLIR
+    poDS->m_bByteOrderIsLittleEndian = CPLTestBool(CSLFetchNameValueDef(
+        poOpenInfo->papszOpenOptions, "BYTE_ORDER_LITTLE_ENDIAN", "NO"));
+
     return poDS;
 }
 

frmts/png/pngdataset.cpp

@@ -113,6 +113,8 @@ class PNGDataset final : public GDALPamDataset
     int bHasReadICCMetadata;
     void LoadICCProfile();
 
+    bool m_bByteOrderIsLittleEndian = false;
+
     static void WriteMetadataAsText(jmp_buf sSetJmpContext, png_structp hPNG,
                                     png_infop psPNGInfo, const char *pszKey,
                                     const char *pszValue);