diff --git a/Makefile b/Makefile

index 3d41182..0fa7517 100644

--- a/Makefile

+++ b/Makefile

@@ -12,6 +12,7 @@ OBJS += $(COCOA_OBJS)

 endif

 STATICLIB = lib/libimagequant.a

+SHAREDLIB = lib/libimagequant.so

 DISTFILES = *.[chm] pngquant.1 Makefile configure README.md INSTALL CHANGELOG COPYRIGHT

 TARNAME = pngquant-$(VERSION)

@@ -32,6 +33,11 @@ staticlib:

 $(STATICLIB): config.mk staticlib

+sharedlib:

+	$(MAKE) -C lib shared

+

+$(SHAREDLIB): config.mk sharedlib

+

 $(OBJS): $(wildcard *.h) config.mk

 rwpng_cocoa.o: rwpng_cocoa.m

@@ -46,6 +52,15 @@ $(TESTBIN): test/test.o $(STATICLIB)

 test: $(BIN) $(TESTBIN)

 	./test/test.sh ./test $(BIN) $(TESTBIN)

+bin.shared: $(OBJS) $(SHAREDLIB)

+	$(CC) $^ $(CFLAGS) $(LDFLAGS) -o $(BIN)

+

+testbin.shared: test/test.o $(SHAREDLIB)

+	$(CC) $^ $(CFLAGS) $(LDFLAGS) -o $(TESTBIN)

+

+test.shared: bin.shared testbin.shared

+	./test/test.sh ./test $(BIN) $(TESTBIN)

+

 dist: $(TARFILE)

 $(TARFILE): $(DISTFILES)

@@ -57,14 +72,15 @@ $(TARFILE): $(DISTFILES)

 	rm -rf $(TARNAME)

 	-shasum $(TARFILE)

-install: $(BIN) pngquant.1

+install: $(BIN) $(BIN).1

 	-mkdir -p '$(BINPREFIX)'

 	-mkdir -p '$(MANPREFIX)/man1'

 	install -m 0755 -p '$(BIN)' '$(BINPREFIX)/$(BIN)'

-	cp pngquant.1 '$(MANPREFIX)/man1/'

+	install -m 0644 -p '$(BIN).1' '$(MANPREFIX)/man1/'

 uninstall:

 	rm -f '$(BINPREFIX)/$(BIN)'

+	rm -f '$(MANPREFIX)/man1/$(BIN).1'

 clean:

 	$(MAKE) -C lib clean

diff --git a/README.md b/README.md

index cbb3e6b..2ddb95d 100644

--- a/README.md

+++ b/README.md

@@ -1,11 +1,11 @@

 #pngquant 2

-This is the official `pngquant` and `libimagequant`.

+[This](https://github.com/pornel/pngquant) is the official `pngquant` and `libimagequant`.

-[pngquant](http://pngquant.org) converts 24/32-bit RGBA PNGs to 8-bit palette with *alpha channel preserved*.

-Such images are compatible with all modern browsers, and a special compatibility setting exists which helps transparency degrade well in Internet Explorer 6.

+[pngquant](https://pngquant.org) converts 24/32-bit RGBA PNGs to 8-bit palette with *alpha channel preserved*.

+Such images are fully standards-compliant and are supported by all web browsers.

-Quantized files are often 40-70% smaller than their 24/32-bit version.

+Quantized files are often 60-80% smaller than their 24/32-bit versions.

 This utility works on Linux, Mac OS X and Windows.

@@ -14,7 +14,7 @@ This utility works on Linux, Mac OS X and Windows.

 - batch conversion of multiple files: `pngquant *.png`

 - Unix-style stdin/stdout chaining: `… | pngquant - | …`

-To further reduce file size, try [optipng](http://optipng.sourceforge.net) or [ImageOptim](http://imageoptim.pornel.net).

+To further reduce file size, try [optipng](http://optipng.sourceforge.net) or [ImageOptim](https://imageoptim.com).

 ##Improvements since 1.0

@@ -28,16 +28,16 @@ Generated files are both smaller and look much better.

   - feedback loop that repeats median cut for poorly quantized colors

   - additional colormap improvement using Voronoi iteration

   - supports much larger number of colors in input images without degradation of quality

-  - gamma correction (output is always generated with gamma 2.2 for web compatibility)

+  - gamma correction and optional color profile support (output is always in gamma 2.2 for web compatibility)

 * More flexible commandline usage

-  - number of colors defaults to 256

+  - number of colors defaults to 256, and can be set automatically with the `--quality` switch

   - long options and standard switches like `--` and `-` are allowed

 * Refactored and modernised code

-  - C99 with no workarounds for old systems

+  - C99 with no workarounds for legacy systems or compilers ([apart from Visual Studio](https://github.com/pornel/pngquant/tree/msvc))

   - floating-point math used throughout

   - Intel SSE optimisations

   - multicore support via OpenMP

@@ -75,7 +75,7 @@ Disables Floyd-Steinberg dithering.

 ###`--floyd=0.5`

-Controls level of dithering (0 = none, 1 = full).

+Controls level of dithering (0 = none, 1 = full). Note that the `=` character is required.

 ###`--posterize bits`

diff --git a/configure b/configure

index 99cf518..12bbb7b 100755

--- a/configure

+++ b/configure

@@ -40,8 +40,8 @@ for i in "$@"; do

         help "--with-lcms2/--without-lcms2  compile with color profile support"

 if [[ "$OSTYPE" =~ "darwin" ]]; then

         help "--with-cocoa/--without-cocoa  use Cocoa framework to read images"

-        help "--with-libpng=<dir>           search for libpng in directory"

 fi

+        help "--with-libpng=<dir>           search for libpng in directory"

         echo

         help "CC=<compiler>                 use given compiler command"

         help "CFLAGS=<flags>                pass options to the compiler"

@@ -102,8 +102,7 @@ fi

         EXTRA_LDFLAGS="$EXTRA_LDFLAGS ${i#*=}"

         ;;

     *)

-        echo "error: unknown switch ${i%%=*} (see $0 --help for the list)"

-        exit 1

+        echo "warning: unknown switch ${i%%=*} (see $0 --help for the list)"

         ;;

     esac

 done

@@ -308,7 +307,13 @@ if [[ "$OSTYPE" =~ "darwin" ]]; then

 fi

 # pairs of possible *.h and lib*.so locations

-DIRS=("/usr/local/include /usr/local/lib"

+DIRS=()

+

+if which -s libpng-config; then

+    DIRS+=("$(libpng-config --prefix) $(libpng-config --libdir)")

+fi

+

+DIRS+=("/usr/local/include /usr/local/lib"

       "/usr/include /usr/lib"

       "/opt/local/include /opt/local/lib" # macports

       )

diff --git a/lib/Makefile b/lib/Makefile

index e4c5693..99448ce 100644

--- a/lib/Makefile

+++ b/lib/Makefile

@@ -1,7 +1,8 @@

 -include config.mk

 STATICLIB=libimagequant.a

-SHAREDLIB=libimagequant.so.0

+SHAREDLIB=libimagequant.so

+SOVER=0

 DLL=libimagequant.dll

 DLLIMP=libimagequant_dll.a

@@ -34,7 +35,8 @@ $(SHAREDOBJS):

 	$(CC) -fPIC $(CFLAGS) -c $(@:.lo=.c) -o $@

 $(SHAREDLIB): $(SHAREDOBJS)

-	$(CC) -shared -o $@ $^ $(LDFLAGS)

+	$(CC) -shared -Wl,-soname,$(SHAREDLIB).$(SOVER) -o $(SHAREDLIB).$(SOVER) $^ $(LDFLAGS)

+	ln -fs $(SHAREDLIB).$(SOVER) $(SHAREDLIB)

 $(OBJS): $(wildcard *.h) config.mk

@@ -49,7 +51,7 @@ $(TARFILE): $(DISTFILES)

 	-shasum $(TARFILE)

 clean:

-	rm -f $(OBJS) $(SHAREDOBJS) $(SHAREDLIB) $(STATICLIB) $(TARFILE) $(DLL) $(DLLIMP) $(DLLDEF)

+	rm -f $(OBJS) $(SHAREDOBJS) $(SHAREDLIB).$(SOVER) $(SHAREDLIB) $(STATICLIB) $(TARFILE) $(DLL) $(DLLIMP) $(DLLDEF)

 distclean: clean

 	rm -f config.mk