add PNG "none" compression mode for disabling png zlib compression

Author: Stéphane Cyr

include/mapcache.h

@@ -1484,6 +1484,7 @@ char* mapcache_util_get_tile_key(mapcache_context *ctx, mapcache_tile *tile, cha
 typedef enum {
   MAPCACHE_COMPRESSION_BEST, /**< best but slowest compression*/
   MAPCACHE_COMPRESSION_FAST, /**< fast compression*/
+  MAPCACHE_COMPRESSION_DISABLE, /**< no compression*/
   MAPCACHE_COMPRESSION_DEFAULT /**< default compression*/
 } mapcache_compression_type;
 

lib/configuration_xml.c

@@ -387,6 +387,8 @@ void parseFormat(mapcache_context *ctx, ezxml_t node, mapcache_cfg *config)
         compression = MAPCACHE_COMPRESSION_FAST;
       } else if(!strcmp(cur_node->txt, "best")) {
         compression = MAPCACHE_COMPRESSION_BEST;
+      } else if(!strcmp(cur_node->txt, "none")) {
+        compression = MAPCACHE_COMPRESSION_DISABLE;
       } else {
         ctx->set_error(ctx, 400, "unknown compression type %s for format \"%s\"", cur_node->txt, name);
         return;

lib/imageio_png.c

@@ -45,6 +45,9 @@ typedef unsigned long int uint64_t;
 #ifndef Z_BEST_COMPRESSION
 #define Z_BEST_COMPRESSION 9
 #endif
+#ifndef Z_NO_COMPRESSION
+#define Z_NO_COMPRESSION 0
+#endif
 
 /* Table of CRCs of all 8-bit messages. */
 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
@@ -410,6 +413,9 @@ mapcache_buffer* _mapcache_imageio_png_encode(mapcache_context *ctx, mapcache_im
     png_set_compression_level (png_ptr, Z_BEST_COMPRESSION);
   else if(compression == MAPCACHE_COMPRESSION_FAST)
     png_set_compression_level (png_ptr, Z_BEST_SPEED);
+  else if(compression == MAPCACHE_COMPRESSION_DISABLE)
+    png_set_compression_level (png_ptr, Z_NO_COMPRESSION);
+    
   png_set_filter(png_ptr,0,PNG_FILTER_NONE);
 
   info_ptr = png_create_info_struct(png_ptr);
@@ -1314,6 +1320,8 @@ mapcache_buffer* _mapcache_imageio_png_q_encode( mapcache_context *ctx, mapcache
     png_set_compression_level (png_ptr, Z_BEST_COMPRESSION);
   else if(compression == MAPCACHE_COMPRESSION_FAST)
     png_set_compression_level (png_ptr, Z_BEST_SPEED);
+  else if(compression == MAPCACHE_COMPRESSION_DISABLE)
+    png_set_compression_level (png_ptr, Z_NO_COMPRESSION);
   png_set_filter(png_ptr,0,PNG_FILTER_NONE);
   info_ptr = png_create_info_struct(png_ptr);
   if (!info_ptr) {