ZopfliPNG

Author: lvandeve

README

@@ -25,5 +25,8 @@ zopfli_bin.c is separate from the library and contains an example program to
 create very well compressed gzip files. Currently the makefile builds this
 program with the library statically linked in.
 
+To build the binary, use "make". To build the library as a shared Linux library,
+use "make libzopfli". The source code of Zopfli is under src/zopfli.
+
 Zopfli Compression Algorithm was created by Lode Vandevenne and Jyrki
 Alakuijala, based on an algorithm by Jyrki Alakuijala.

README.zopflipng

@@ -0,0 +1,35 @@
+ZopfliPNG is a command line program to optimize the Portable Network Graphics
+(PNG) images. This version has the following features:
+- uses Zopfli compression for the Deflate compression,
+- compares several strategies for choosing scanline filter codes,
+- chooses a suitable color type to losslessly encode the image,
+- removes all chunks that are unimportant for the typical web use (metadata,
+  text, etc...),
+- optionally alters the hidden colors of fully transparent pixels for more
+  compression, and,
+- optionally converts 16-bit color channels to 8-bit.
+
+This is an alpha-release for testing while improvements, particularly to add
+palette selection, are still being made. Feedback and bug reports are welcome.
+
+To build ZopfliPNG, use "make zopflipng", or compile all the sources except
+zopfli_bin.c.
+
+The main compression algorithm in ZopfliPNG is ported from WebP lossless, but
+naturally cannot give as much compression gain for PNGs as it does for a more
+modern compression codec like WebP
+https://developers.google.com/speed/webp/docs/webp_lossless_bitstream_specification.
+
+Compared to libpng -- an often used PNG encoder implementation -- ZopfliPNG uses
+2-3 orders of magnitude more CPU time for compression. Initial testing using a
+corpus of 1000 PNGs with translucency, randomly selected from the internet,
+gives a compression improvement of 12% compared to convert -q 95, but only 0.5%
+compared to pngout (from better of /f0 and /f5 runs).
+
+By releasing this software we hope to make images on the web load faster without
+a new image format, but the opportunities for optimization within PNG are
+limited. When targeting Android, Chrome, Opera, and Yandex browsers, or by using
+suitable plugins for other browsers, it is good to note that WebP lossless
+images are still 26 % smaller than images recompressed with ZopfliPNG.
+
+2013-05-07, Lode Vandevenne and Jyrki Alakuijala

makefile

@@ -1,5 +1,37 @@
-make:
-	gcc src/zopfli/*.c -O2 -W -Wall -Wextra -ansi -pedantic -lm -o zopfli
+CC = gcc
+CXX = g++
 
-debug:
-	gcc src/zopfli/*.c -g3 -lm -o zopfli
+CFLAGS = -W -Wall -Wextra -ansi -pedantic -lm -O2
+CXXFLAGS = -W -Wall -Wextra -ansi -pedantic -O2
+
+ZOPFLILIB_SRC = src/zopfli/blocksplitter.c src/zopfli/cache.c\
+                src/zopfli/deflate.c src/zopfli/gzip_container.c\
+                src/zopfli/hash.c src/zopfli/katajainen.c\
+                src/zopfli/lz77.c src/zopfli/squeeze.c\
+                src/zopfli/tree.c src/zopfli/util.c\
+                src/zopfli/zlib_container.c src/zopfli/zopfli_lib.c
+ZOPFLILIB_OBJ := $(patsubst src/zopfli/%.c,%.o,$(ZOPFLILIB_SRC))
+ZOPFLIBIN_SRC := src/zopfli/zopfli_bin.c
+LODEPNG_SRC := src/zopflipng/lodepng/lodepng.cpp src/zopflipng/lodepng/lodepng_util.cpp
+ZOPFLIPNGLIB_SRC := src/zopflipng/zopflipng_lib.cc
+ZOPFLIPNGBIN_SRC := src/zopflipng/zopflipng_bin.cc
+
+.PHONY: zopfli zopflipng
+
+# Zopfli binary
+zopfli:
+	$(CC) $(ZOPFLILIB_SRC) $(ZOPFLIBIN_SRC) $(CFLAGS) -o zopfli
+
+# Zopfli shared library
+libzopfli:
+	$(CC) $(ZOPFLILIB_SRC) $(CFLAGS) -fPIC -c
+	$(CC) $(ZOPFLILIB_OBJ) $(CFLAGS) -shared -Wl,-soname,libzopfli.so.1 -o libzopfli.so.1.0.1
+
+# ZopfliPNG binary
+zopflipng:
+	$(CC) $(ZOPFLILIB_SRC) $(CFLAGS) -c
+	$(CXX) $(ZOPFLILIB_OBJ) $(LODEPNG_SRC) $(ZOPFLIPNGLIB_SRC) $(ZOPFLIPNGBIN_SRC) $(CFLAGS) -o zopflipng
+
+# Remove all libraries and binaries
+clean:
+	rm -f zopflipng zopfli $(ZOPFLILIB_OBJ) libzopfli*

src/zopfli/deflate.h

@@ -27,6 +27,10 @@ Functions to compress according to the DEFLATE specification, using the
 
 #include "zopfli.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
 Compresses according to the deflate specification and append the compressed
 result to the output.
@@ -74,4 +78,9 @@ lend: end of block (not inclusive)
 double ZopfliCalculateBlockSize(const unsigned short* litlens,
                                 const unsigned short* dists,
                                 size_t lstart, size_t lend, int btype);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif  /* ZOPFLI_DEFLATE_H_ */

src/zopfli/gzip_container.h

@@ -26,6 +26,10 @@ Functions to compress according to the Gzip specification.
 
 #include "zopfli.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
 Compresses according to the gzip specification and append the compressed
 result to the output.
@@ -39,4 +43,8 @@ void ZopfliGzipCompress(const ZopfliOptions* options,
                         const unsigned char* in, size_t insize,
                         unsigned char** out, size_t* outsize);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif  /* ZOPFLI_GZIP_H_ */

src/zopfli/zlib_container.h

@@ -26,6 +26,10 @@ Functions to compress according to the Zlib specification.
 
 #include "zopfli.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
 Compresses according to the zlib specification and append the compressed
 result to the output.
@@ -39,4 +43,8 @@ void ZopfliZlibCompress(const ZopfliOptions* options,
                         const unsigned char* in, size_t insize,
                         unsigned char** out, size_t* outsize);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif  /* ZOPFLI_ZLIB_H_ */

src/zopfli/zopfli.h

@@ -23,6 +23,10 @@ Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
 #include <stddef.h>
 #include <stdlib.h> /* for size_t */
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
 Options used throughout the program.
 */
@@ -86,4 +90,8 @@ void ZopfliCompress(const ZopfliOptions* options, ZopfliFormat output_type,
                     const unsigned char* in, size_t insize,
                     unsigned char** out, size_t* outsize);
 
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
 #endif  /* ZOPFLI_ZOPFLI_H_ */