perf(cli): reduce libpng compression level to 6

zlib compression hits heavy diminishing returns after level 6 according to benchmarks like https://aws.amazon.com/blogs/opensource/improving-zlib-cloudflare-and-comparing-performance-with-other-zlib-forks/ and https://facebook.github.io/zstd/. Compression at level 7–9 keeps getting slower with little impact on size. HiColor currently uses 9. zlib will not match OptiPNG and Oxipng in any case. Let's use level 6 to recover the performance of v0.5.0. v0.6.1
dbohdan · Oct 5, 2024 · 30e4621 · 30e4621
1 parent 31b83ef
commit 30e4621
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diff --git a/README.md b/README.md
@@ -92,7 +92,7 @@ Use `quantize` to create high-color images readable by other programs.
 `info` prints information about a HiColor file: version (`5` for 15-bit or `6` for 16), width, and height.
 
 ```none
-HiColor 0.6.0
+HiColor 0.6.1
 Create 15/16-bit color RGB images.
 
 usage:

diff --git a/cli.c b/cli.c
@@ -16,6 +16,7 @@
 
 #define HICOLOR_CLI_ERROR "error: "
 #define HICOLOR_CLI_LIB_NAME_FORMAT "%-9s"
+#define HICOLOR_CLI_LIBPNG_COMPRESSION_LEVEL 6
 #define HICOLOR_CLI_NO_MEMORY_EXIT_CODE 255
 
 #define HICOLOR_CLI_CMD_ENCODE "encode"
@@ -197,7 +198,7 @@ bool save_png(
         PNG_COMPRESSION_TYPE_DEFAULT,
         PNG_FILTER_TYPE_DEFAULT
     );
-    png_set_compression_level(png, 9);
+    png_set_compression_level(png, HICOLOR_CLI_LIBPNG_COMPRESSION_LEVEL);
     png_write_info(png, info);
 
     png_bytep row = malloc(png_get_rowbytes(png, info));

diff --git a/hicolor.h b/hicolor.h
@@ -19,7 +19,7 @@
 #include <stdio.h>
 
 #define HICOLOR_BAYER_SIZE 8
-#define HICOLOR_LIBRARY_VERSION 600
+#define HICOLOR_LIBRARY_VERSION 601
 
 /* Types. */