Merge pull request #25280 from Kumataro:fix25274

imgcodecs: jpeg: re-support to read CMYK Jpeg #25280

Close #25274 
OpenCV Extra: https://github.com/opencv/opencv_extra/pull/1163

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/imgcodecs/src/grfmt_jpeg.cpp

@@ -402,16 +402,12 @@ int my_jpeg_load_dht (struct jpeg_decompress_struct *info, unsigned char *dht,
 bool  JpegDecoder::readData( Mat& img )
 {
     volatile bool result = false;
-    size_t step = img.step;
-    bool color = img.channels() > 1;
+    const bool color = img.channels() > 1;
 
     if( m_state && m_width && m_height )
     {
         jpeg_decompress_struct* cinfo = &((JpegState*)m_state)->cinfo;
         JpegErrorMgr* jerr = &((JpegState*)m_state)->jerr;
-#ifndef JCS_EXTENSIONS
-        JSAMPARRAY buffer = 0;
-#endif
 
         if( setjmp( jerr->setjmp_buffer ) == 0 )
         {
@@ -431,29 +427,30 @@ bool  JpegDecoder::readData( Mat& img )
             }
 #endif
 
-#ifdef JCS_EXTENSIONS
+            // See https://github.com/opencv/opencv/issues/25274
+            // Conversion CMYK->BGR is not supported in libjpeg-turbo.
+            // So supporting both directly and indirectly is necessary.
+            bool doDirectRead = false;
+
             if( color )
             {
+                if( cinfo->num_components != 4 )
+                {
+#ifdef JCS_EXTENSIONS
                     cinfo->out_color_space = JCS_EXT_BGR;
                     cinfo->out_color_components = 3;
-            }
-            else
-            {
-                cinfo->out_color_space = JCS_GRAYSCALE;
-                cinfo->out_color_components = 1;
-            }
+                    doDirectRead = true; // BGR -> BGR
 #else
-            if( color )
-            {
-                if( cinfo->num_components != 4 )
-                {
                     cinfo->out_color_space = JCS_RGB;
                     cinfo->out_color_components = 3;
+                    doDirectRead = false; // RGB -> BGR
+#endif
                 }
                 else
                 {
                     cinfo->out_color_space = JCS_CMYK;
                     cinfo->out_color_components = 4;
+                    doDirectRead = false; // CMYK -> BGR
                 }
             }
             else
@@ -462,14 +459,15 @@ bool  JpegDecoder::readData( Mat& img )
                 {
                     cinfo->out_color_space = JCS_GRAYSCALE;
                     cinfo->out_color_components = 1;
+                    doDirectRead = true; // GRAY -> GRAY
                 }
                 else
                 {
                     cinfo->out_color_space = JCS_CMYK;
                     cinfo->out_color_components = 4;
+                    doDirectRead = false; // CMYK -> GRAY
                 }
             }
-#endif
 
             // Check for Exif marker APP1
             jpeg_saved_marker_ptr exif_marker = NULL;
@@ -496,18 +494,24 @@ bool  JpegDecoder::readData( Mat& img )
 
             jpeg_start_decompress( cinfo );
 
-#ifndef JCS_EXTENSIONS
-            buffer = (*cinfo->mem->alloc_sarray)((j_common_ptr)cinfo,
+            if( doDirectRead)
+            {
+                for( int iy = 0 ; iy < m_height; iy ++ )
+                {
+                    uchar* data = img.ptr<uchar>(iy);
+                    jpeg_read_scanlines( cinfo, &data, 1 );
+                }
+            }
+            else
+            {
+                JSAMPARRAY buffer = (*cinfo->mem->alloc_sarray)((j_common_ptr)cinfo,
                                                                  JPOOL_IMAGE, m_width*4, 1 );
-#endif
 
-            uchar* data = img.ptr();
-            for( ; m_height--; data += step )
+                for( int iy = 0 ; iy < m_height; iy ++ )
                 {
-#ifdef JCS_EXTENSIONS
-                jpeg_read_scanlines( cinfo, &data, 1 );
-#else
+                    uchar* data = img.ptr<uchar>(iy);
                     jpeg_read_scanlines( cinfo, buffer, 1 );
+
                     if( color )
                     {
                         if( cinfo->out_color_components == 3 )
@@ -522,7 +526,7 @@ bool  JpegDecoder::readData( Mat& img )
                         else
                             icvCvt_CMYK2Gray_8u_C4C1R( buffer[0], 0, data, 0, Size(m_width,1) );
                     }
-#endif
+                }
             }
 
             result = true;

modules/imgcodecs/test/test_jpeg.cpp

@@ -178,6 +178,44 @@ TEST(Imgcodecs_Jpeg, encode_decode_rst_jpeg)
     EXPECT_EQ(0, remove(output_normal.c_str()));
 }
 
+// See https://github.com/opencv/opencv/issues/25274
+typedef testing::TestWithParam<int> Imgcodecs_Jpeg_decode_cmyk;
+TEST_P(Imgcodecs_Jpeg_decode_cmyk, regression25274)
+{
+    const int imread_flag = GetParam();
+
+    /*
+     * "test_1_c4.jpg" is CMYK-JPEG.
+     * $ convert test_1_c3.jpg -colorspace CMYK test_1_c4.jpg
+     * $ identify test_1_c4.jpg
+     * test_1_c4.jpg JPEG 480x640 480x640+0+0 8-bit CMYK 11240B 0.000u 0:00.000
+     */
+
+    cvtest::TS& ts = *cvtest::TS::ptr();
+
+    string  rgb_filename  = string(ts.get_data_path()) + "readwrite/test_1_c3.jpg";
+    cv::Mat rgb_img       = cv::imread(rgb_filename, imread_flag);
+    ASSERT_FALSE(rgb_img.empty());
+
+    string  cmyk_filename = string(ts.get_data_path()) + "readwrite/test_1_c4.jpg";
+    cv::Mat cmyk_img      = cv::imread(cmyk_filename, imread_flag);
+    ASSERT_FALSE(cmyk_img.empty());
+
+    EXPECT_EQ(rgb_img.size(), cmyk_img.size());
+    EXPECT_EQ(rgb_img.type(), cmyk_img.type());
+
+    // Jpeg is lossy compression.
+    // There may be small differences in decoding results by environments.
+    // -> 255 * 1% = 2.55 .
+    EXPECT_EQ(3, cvtest::norm(rgb_img, cmyk_img, NORM_INF));
+}
+
+INSTANTIATE_TEST_CASE_P( /* nothing */,
+                        Imgcodecs_Jpeg_decode_cmyk,
+                        testing::Values(cv::IMREAD_COLOR,
+                                        cv::IMREAD_GRAYSCALE,
+                                        cv::IMREAD_ANYCOLOR));
+
 //==================================================================================================
 
 static const uint32_t default_sampling_factor = static_cast<uint32_t>(0x221111);