Detect libpng

Makefile.am

@@ -108,13 +108,19 @@ endif
 
 
 cjpeg_SOURCES = cdjpeg.h cderror.h cdjpeg.c cjpeg.c rdbmp.c rdgif.c \
-	rdppm.c rdswitch.c rdtarga.c rdjpeg.c rdpng.c
+	rdppm.c rdswitch.c rdtarga.c rdjpeg.c
 
 cjpeg_LDADD = libjpeg.la
 
 cjpeg_CFLAGS = -DBMP_SUPPORTED -DGIF_SUPPORTED -DPPM_SUPPORTED \
 	-DTARGA_SUPPORTED
 
+if HAVE_LIBPNG
+cjpeg_CFLAGS += -DPNG_SUPPORTED $(libpng_CFLAGS)
+cjpeg_LDADD += $(libpng_LIBS)
+cjpeg_SOURCES += rdpng.c
+endif
+
 djpeg_SOURCES = cdjpeg.h cderror.h cdjpeg.c djpeg.c rdcolmap.c rdswitch.c \
 	wrbmp.c wrgif.c wrppm.c wrtarga.c
 

configure.ac

@@ -95,6 +95,11 @@ fi
 # Checks for libraries.
 AC_CHECK_LIB([m],[pow])
 
+PKG_CHECK_MODULES([libpng], [libpng], [HAVE_LIBPNG=1], [
+  PKG_CHECK_MODULES([libpng], [libpng12], [HAVE_LIBPNG=1], [HAVE_LIBPNG=0])
+])
+AM_CONDITIONAL([HAVE_LIBPNG], [test "$HAVE_LIBPNG" -eq 1])
+
 # Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS([stddef.h stdlib.h string.h])