pngquant

# install libpng15
# ----------------

./configure --prefix=/usr/local/libpng
make check
sudo make install
make check

#
sudo updatedb
locate libpng (locate the ".../libpng15.so.15" line and COPY)
sudo ln -s /usr/local/libpng/lib/libpng15.so.15 /usr/lib/libpng15.so.15

# pngquant/config.mk
# ------------------

# auto-generated by configure
PREFIX = /usr/local
VERSION = 2.3.1
CC = gcc
CFLAGS = -O3 -fno-math-errno -funroll-loops -fomit-frame-pointer -Wall -std=c99 -I. -DNDEBUG -DUSE_SSE=1 -msse -Wno-unknown-pragmas -I/usr/local/libpng/include/libpng15 -I/usr/include
LDFLAGS =  -lm lib/libimagequant.a -L/usr/local/libpng/lib -lpng15   -lz   -lm
COCOA_READER = 0

#

make
sudo make install