Merge pull request #27551 from sturkmen72:png-improvements

Add enum IMWRITE_PNG_ZLIBBUFFER_SIZE #27551

### Pull Request Readiness Checklist

This patch enables users to set the internal zlib compression buffer size for PNG encoding

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
- [ ] 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.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/imgcodecs/include/opencv2/imgcodecs.hpp

@@ -94,9 +94,10 @@ enum ImwriteFlags {
        IMWRITE_JPEG_CHROMA_QUALITY = 6,  //!< Separate chroma quality level, 0 - 100, default is -1 - don't use. If JPEG_LIB_VERSION < 70, Not supported.
        IMWRITE_JPEG_SAMPLING_FACTOR = 7, //!< For JPEG, set sampling factor. See cv::ImwriteJPEGSamplingFactorParams.
        IMWRITE_PNG_COMPRESSION     = 16, //!< For PNG, it can be the compression level from 0 to 9. A higher value means a smaller size and longer compression time. If specified, strategy is changed to IMWRITE_PNG_STRATEGY_DEFAULT (Z_DEFAULT_STRATEGY). Default value is 1 (best speed setting).
-       IMWRITE_PNG_STRATEGY        = 17, //!< One of cv::ImwritePNGFlags, default is IMWRITE_PNG_STRATEGY_RLE.
+       IMWRITE_PNG_STRATEGY        = 17, //!< For PNG, One of cv::ImwritePNGFlags, default is IMWRITE_PNG_STRATEGY_RLE.
-       IMWRITE_PNG_BILEVEL         = 18, //!< Binary level PNG, 0 or 1, default is 0.
+       IMWRITE_PNG_BILEVEL         = 18, //!< For PNG, Binary level PNG, 0 or 1, default is 0.
-       IMWRITE_PNG_FILTER          = 19, //!< One of cv::ImwritePNGFilterFlags, default is IMWRITE_PNG_FILTER_SUB.
+       IMWRITE_PNG_FILTER          = 19, //!< For PNG, One of cv::ImwritePNGFilterFlags, default is IMWRITE_PNG_FILTER_SUB.
+       IMWRITE_PNG_ZLIBBUFFER_SIZE = 20, //!< For PNG, sets the size of the internal zlib compression buffer in bytes.
        IMWRITE_PXM_BINARY          = 32, //!< For PPM, PGM, or PBM, it can be a binary format flag, 0 or 1. Default value is 1.
        IMWRITE_EXR_TYPE            = (3 << 4) + 0 /* 48 */, //!< override EXR storage type (FLOAT (FP32) is default)
        IMWRITE_EXR_COMPRESSION     = (3 << 4) + 1 /* 49 */, //!< override EXR compression type (ZIP_COMPRESSION = 3 is default)

modules/imgcodecs/src/grfmt_png.cpp

@@ -947,26 +947,36 @@ bool  PngEncoder::write( const Mat& img, const std::vector<int>& params )
 
                 for( size_t i = 0; i < params.size(); i += 2 )
                 {
-                    if( params[i] == IMWRITE_PNG_COMPRESSION )
+                    switch (params[i])
                     {
+                    case IMWRITE_PNG_COMPRESSION:
                         m_compression_strategy = IMWRITE_PNG_STRATEGY_DEFAULT; // Default strategy
                         m_compression_level = params[i+1];
                         m_compression_level = MIN(MAX(m_compression_level, 0), Z_BEST_COMPRESSION);
                         set_compression_level = true;
-                    }
+                        break;
-                    if( params[i] == IMWRITE_PNG_STRATEGY )
+
-                    {
+                    case IMWRITE_PNG_STRATEGY:
                         m_compression_strategy = params[i+1];
                         m_compression_strategy = MIN(MAX(m_compression_strategy, 0), Z_FIXED);
-                    }
+                        break;
-                    if( params[i] == IMWRITE_PNG_BILEVEL )
+
-                    {
+                    case IMWRITE_PNG_BILEVEL:
                         m_isBilevel = params[i+1] != 0;
-                    }
+                        break;
-                    if( params[i] == IMWRITE_PNG_FILTER )
+
-                    {
+                    case IMWRITE_PNG_FILTER:
                         m_filter = params[i+1];
                         set_filter = true;
+                        break;
+
+                    case IMWRITE_PNG_ZLIBBUFFER_SIZE:
+                        png_set_compression_buffer_size(png_ptr, params[i+1]);
+                        break;
+
+                    default:
+                        CV_LOG_WARNING(NULL, "An unknown or unsupported ImwriteFlags value was specified and has been ignored.");
+                        break;
                     }
                 }
 

modules/imgcodecs/test/test_png.cpp

@@ -12,14 +12,15 @@ TEST(Imgcodecs_Png, write_big)
 {
     const string root = cvtest::TS::ptr()->get_data_path();
     const string filename = root + "readwrite/read.png";
-    const string dst_file = cv::tempfile(".png");
     Mat img;
     ASSERT_NO_THROW(img = imread(filename));
     ASSERT_FALSE(img.empty());
     EXPECT_EQ(13043, img.cols);
     EXPECT_EQ(13917, img.rows);
-    ASSERT_NO_THROW(imwrite(dst_file, img));
+
-    EXPECT_EQ(0, remove(dst_file.c_str()));
+    vector<uchar> buff;
+    ASSERT_NO_THROW(imencode(".png", img, buff, { IMWRITE_PNG_ZLIBBUFFER_SIZE, INT_MAX }));
+    EXPECT_EQ((size_t)816219, buff.size());
 }
 
 TEST(Imgcodecs_Png, encode)