[devel] Added PNG_WRITE_OPTIMIZE_CMF_SUPPORTED macro to make zlib "CMF"

optimization configureable.

ANNOUNCE

@@ -87,6 +87,8 @@ Version 1.5.3beta05 [May 5, 2011]
     requiring the host OS to implement snprintf.  As a side effect the
     dependency of the tIME-supporting RFC1132 code on stdio is removed and
     PNG_NO_WARNINGS does actually work now.
+  Added PNG_WRITE_OPTIMIZE_CMF_SUPPORTED macro to make the zlib "CMF" byte
+    optimization configureable.
 
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CHANGES

@@ -3346,6 +3346,8 @@ Version 1.5.3beta05 [May 5, 2011]
     requiring the host OS to implement snprintf.  As a side effect the
     dependency of the tIME-supporting RFC1132 code on stdio is removed and
     PNG_NO_WARNINGS does actually work now.
+  Added PNG_WRITE_OPTIMIZE_CMF_SUPPORTED macro to make the zlib "CMF" byte
+    optimization configureable.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

pngwutil.c

@@ -447,6 +447,7 @@ png_write_compressed_data_out(png_structp png_ptr, compression_state *comp)
       return;
    }
 
+#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
    if (comp->input_len >= 2 && comp->input_len < 16384)
    {
       unsigned int z_cmf;  /* zlib compression method and flags */
@@ -464,12 +465,12 @@ png_write_compressed_data_out(png_structp png_ptr, compression_state *comp)
       {
          unsigned int z_cinfo;
          unsigned int half_z_window_size;
-         png_size_t uncompressed_idat_size = comp->input_len;
+         png_size_t uncompressed_text_size = comp->input_len;
 
          z_cinfo = z_cmf >> 4;
          half_z_window_size = 1 << (z_cinfo + 7);
 
-         while (uncompressed_idat_size <= half_z_window_size &&
+         while (uncompressed_text_size <= half_z_window_size &&
              half_z_window_size >= 256)
          {
             z_cinfo--;
@@ -506,6 +507,7 @@ png_write_compressed_data_out(png_structp png_ptr, compression_state *comp)
          png_error(png_ptr,
              "Invalid zlib compression method or flags in non-IDAT chunk");
    }
+#endif /* PNG_WRITE_OPTIMIZE_CMF_SUPPORTED */
 
    /* Write saved output buffers, if any */
    for (i = 0; i < comp->num_output_ptr; i++)
@@ -838,7 +840,9 @@ png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
    if (!(png_ptr->mode & PNG_HAVE_IDAT) &&
        png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
    {
+#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
       unsigned int z_cmf;  /* zlib compression method and flags */
+#endif /* PNG_WRITE_OPTIMIZE_CMF_SUPPORTED */
 
 #ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
       int ret;
@@ -880,6 +884,7 @@ png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
        */
       png_ptr->zstream.data_type = Z_BINARY;
 
+#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
       /* Optimize the CMF field in the zlib stream.  This hack of the zlib
        * stream is compliant to the stream specification.
        */
@@ -941,6 +946,7 @@ png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
       else
          png_error(png_ptr,
              "Invalid zlib compression method or flags in IDAT");
+#endif /* PNG_WRITE_OPTIMIZE_CMF_SUPPORTED */
    }
 
    png_write_chunk(png_ptr, png_IDAT, data, length);

scripts/pnglibconf.dfa

@@ -6,7 +6,7 @@
 #
 com pnglibconf.h - library build configuration
 com
-com libpng version 1.5.0 - January 6, 2011
+com libpng version 1.5.3 -  (PENDING RELEASE)
 com
 com Copyright (c) 1998-2011 Glenn Randers-Pehrson
 com
@@ -550,6 +550,9 @@ option SAVE_INT_32 requires WRITE
 
 # png_save_int_32 is required by the ancillary chunks oFFs and pCAL
 
+# added at libpng-1.5.3
+option WRITE_OPTIMIZE_CMF requires WRITE
+
 option READ_iCCP enables READ_COMPRESSED_TEXT
 option READ_iTXt enables READ_COMPRESSED_TEXT
 option READ_zTXt enables READ_COMPRESSED_TEXT
@@ -563,6 +566,7 @@ option WRITE_iTXt enables WRITE_COMPRESSED_TEXT
 option WRITE_zTXt enables WRITE_COMPRESSED_TEXT
 option WRITE_COMPRESSED_TEXT enables WRITE_TEXT
 
+
 # Turn this off to disable png_read_png() and png_write_png() and
 # leave the row_pointers member out of the info structure.
 

scripts/pnglibconf.h.prebuilt

@@ -156,6 +156,7 @@
 #define PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION
 #define PNG_WRITE_iTXt_SUPPORTED
 #define PNG_WRITE_oFFs_SUPPORTED
+#define PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
 #define PNG_WRITE_PACK_SUPPORTED
 #define PNG_WRITE_PACKSWAP_SUPPORTED
 #define PNG_WRITE_pCAL_SUPPORTED