imgcodecs: png: adjust value range for IMWRITE_PNG_ZLIBBUFFER_SIZE

modules/imgcodecs/src/grfmt_png.cpp

@@ -1007,7 +1007,11 @@ bool  PngEncoder::write( const Mat& img, const std::vector<int>& params )
                         break;
 
                     case IMWRITE_PNG_ZLIBBUFFER_SIZE:
-                        png_set_compression_buffer_size(png_ptr, params[i+1]);
+                        // The default value is 8 KiB.
+                        // The minimum limit is 6, which is from from https://github.com/opencv/opencv/blob/4.12.0/3rdparty/libpng/pngset.c#L1600 .
+                        // The maximum limit is 1 MiB, which has been provisionally set. libpng limitation is 2 GiB(INT32_MAX), but it is too large.
+                        // For normal use, 128 or 256 KiB may be sufficient. See https://zlib.net/zlib_how.html .
+                        png_set_compression_buffer_size(png_ptr, MIN(MAX(params[i+1],6), 1024*1024));
                         break;
 
                     default:

modules/imgcodecs/src/grfmt_spng.cpp

@@ -23,6 +23,7 @@
 #include <zlib.h>
 
 #include "grfmt_spng.hpp"
+#include <opencv2/core/utils/logger.hpp>
 
 /*
  * libspng does not support RGB -> Gray conversion. In order to decode colorful images as grayscale
@@ -554,6 +555,11 @@ bool SPngEncoder::write(const Mat &img, const std::vector<int> &params)
                 filter = params[i+1];
                 set_filter = true;
             }
+            if( params[i] == IMWRITE_PNG_ZLIBBUFFER_SIZE )
+            {
+                // See https://libspng.org/docs/migrate-libpng/#miscellaneous-functions
+                CV_LOG_WARNING(nullptr, "libspng does not support png_set_compression_buffer_size() which is required for IMWRITE_PNG_ZLIBBUFFER_SIZE");
+            }
         }
 
         ihdr.bit_depth = depth == CV_8U ? isBilevel ? 1 : 8 : 16;