Merge pull request #20875 from Harvey-Huang:master

* bmp specified BI_BITFIELDS should take care RGBA bit mask

* change the name

* support xrgb bmp file

* support xrgb bmp file(add test case)

* update testing code

modules/imgcodecs/src/grfmt_bmp.cpp

@@ -58,6 +58,7 @@ BmpDecoder::BmpDecoder()
     m_origin = ORIGIN_TL;
     m_bpp = 0;
     m_rle_code = BMP_RGB;
+    initMask();
 }
 
 
@@ -97,6 +98,7 @@ bool  BmpDecoder::readHeader()
         int  size = m_strm.getDWord();
         CV_Assert(size > 0); // overflow, 2Gb limit
 
+        initMask();
         if( size >= 36 )
         {
             m_width  = m_strm.getDWord();
@@ -107,7 +109,30 @@ bool  BmpDecoder::readHeader()
             m_rle_code = (BmpCompression)m_rle_code_;
             m_strm.skip(12);
             int clrused = m_strm.getDWord();
-            m_strm.skip( size - 36 );
+
+            if( m_bpp == 32 && m_rle_code == BMP_BITFIELDS && size >= 56 )
+            {
+                m_strm.skip(4); //important colors
+                //0 is Red channel bit mask, 1 is Green channel bit mask, 2 is Blue channel bit mask, 3 is Alpha channel bit mask
+                for( int index_rgba = 0; index_rgba < 4; ++index_rgba )
+                {
+                    uint mask = m_strm.getDWord();
+                    m_rgba_mask[index_rgba] = mask;
+                    if(mask != 0)
+                    {
+                        int bit_count = 0;
+                        while(!(mask & 1))
+                        {
+                            mask >>= 1;
+                            ++bit_count;
+                        }
+                        m_rgba_bit_offset[index_rgba] = bit_count;
+                    }
+                }
+                m_strm.skip( size - 56 );
+            }
+            else
+                m_strm.skip( size - 36 );
 
             if( m_width > 0 && m_height != 0 &&
              (((m_bpp == 1 || m_bpp == 4 || m_bpp == 8 ||
@@ -486,8 +511,14 @@ decode_rle8_bad: ;
                     icvCvt_BGRA2Gray_8u_C4C1R( src, 0, data, 0, Size(m_width,1) );
                 else if( img.channels() == 3 )
                     icvCvt_BGRA2BGR_8u_C4C3R(src, 0, data, 0, Size(m_width, 1));
-                else if( img.channels() == 4 )
-                    memcpy(data, src, m_width * 4);
+                else if ( img.channels() == 4 )
+                {
+                    bool has_bit_mask = (m_rgba_bit_offset[0] >= 0) && (m_rgba_bit_offset[1] >= 0) && (m_rgba_bit_offset[2] >= 0);
+                    if ( has_bit_mask )
+                        maskBGRA(data, src, m_width);
+                    else
+                        memcpy(data, src, m_width * 4);
+                }
             }
             result = true;
             break;
@@ -503,7 +534,26 @@ decode_rle8_bad: ;
     return result;
 }
 
+void  BmpDecoder::initMask()
+{
+    memset(m_rgba_mask, 0, sizeof(m_rgba_mask));
+    memset(m_rgba_bit_offset, -1, sizeof(m_rgba_bit_offset));
+}
 
+void  BmpDecoder::maskBGRA(uchar* des, uchar* src, int num)
+{
+    for( int i = 0; i < num; i++, des += 4, src += 4 )
+    {
+        uint data = *((uint*)src);
+        des[0] = (uchar)((m_rgba_mask[2] & data) >> m_rgba_bit_offset[2]);
+        des[1] = (uchar)((m_rgba_mask[1] & data) >> m_rgba_bit_offset[1]);
+        des[2] = (uchar)((m_rgba_mask[0] & data) >> m_rgba_bit_offset[0]);
+        if (m_rgba_bit_offset[3] >= 0)
+            des[3] = (uchar)((m_rgba_mask[3] & data) >> m_rgba_bit_offset[3]);
+        else
+            des[3] = 255;
+    }
+}
 //////////////////////////////////////////////////////////////////////////////////////////
 
 BmpEncoder::BmpEncoder()

modules/imgcodecs/src/grfmt_bmp.hpp

@@ -73,6 +73,9 @@ public:
 
 protected:
 
+    void  initMask();
+    void  maskBGRA(uchar* des, uchar* src, int num);
+
     enum Origin
     {
         ORIGIN_TL = 0,
@@ -85,6 +88,8 @@ protected:
     int             m_bpp;
     int             m_offset;
     BmpCompression  m_rle_code;
+    uint            m_rgba_mask[4];
+    int             m_rgba_bit_offset[4];
 };
 
 

modules/imgcodecs/test/test_grfmt.cpp

@@ -295,6 +295,32 @@ TEST(Imgcodecs_Bmp, read_rle8)
     EXPECT_PRED_FORMAT2(cvtest::MatComparator(0, 0), rle, ord);
 }
 
+TEST(Imgcodecs_Bmp, rgba_bit_mask)
+{
+    const string root = cvtest::TS::ptr()->get_data_path();
+    const string filenameInput = root + "readwrite/test_rgba_mask.bmp";
+
+    const Mat img = cv::imread(filenameInput, IMREAD_UNCHANGED);
+    ASSERT_FALSE(img.empty());
+    ASSERT_EQ(CV_8UC4, img.type());
+
+    const uchar* data = img.ptr();
+    ASSERT_EQ(data[3], 255);
+}
+
+TEST(Imgcodecs_Bmp, read_32bit_xrgb)
+{
+    const string root = cvtest::TS::ptr()->get_data_path();
+    const string filenameInput = root + "readwrite/test_32bit_xrgb.bmp";
+
+    const Mat img = cv::imread(filenameInput, IMREAD_UNCHANGED);
+    ASSERT_FALSE(img.empty());
+    ASSERT_EQ(CV_8UC4, img.type());
+
+    const uchar* data = img.ptr();
+    ASSERT_EQ(data[3], 255);
+}
+
 #ifdef HAVE_IMGCODEC_HDR
 TEST(Imgcodecs_Hdr, regression)
 {