5 files changed, 28 insertions, 7 deletions
diff --git a/libcrystfel/CMakeLists.txt b/libcrystfel/CMakeLists.txt
index aea75b27..69668a8c 100644
--- a/libcrystfel/CMakeLists.txt
+++ b/libcrystfel/CMakeLists.txt
@@ -3,7 +3,7 @@ project(libcrystfel VERSION ${CRYSTFEL_SHORT_VERSION} LANGUAGES C)
 pkg_check_modules(XGANDALF xgandalf)
 pkg_check_modules(PINKINDEXER pinkIndexer)
 pkg_check_modules(FDIP fdip)
-find_package(ZLIB REQUIRED)
+find_package(ZLIB)
 find_package(FLEX REQUIRED)
 find_package(BISON REQUIRED)
 pkg_check_modules(MSGPACK msgpack)
@@ -18,6 +18,7 @@ set(HAVE_PINKINDEXER ${PINKINDEXER_FOUND})
 set(HAVE_FDIP ${FDIP_FOUND})
 set(HAVE_MSGPACK ${MSGPACK_FOUND})
 set(HAVE_LIBCCP4 ${LIBCCP4_FOUND})
+set(HAVE_ZLIB ${ZLIB_FOUND})
 
 # Recent enough version of zlib?
 set(CMAKE_REQUIRED_LIBRARIES "-lz")
diff --git a/libcrystfel/libcrystfel-config.h.cmake.in b/libcrystfel/libcrystfel-config.h.cmake.in
index a7aaaf8f..69fd7397 100644
--- a/libcrystfel/libcrystfel-config.h.cmake.in
+++ b/libcrystfel/libcrystfel-config.h.cmake.in
@@ -5,6 +5,7 @@
 #cmakedefine HAVE_XGANDALF
 #cmakedefine HAVE_PINKINDEXER
 #cmakedefine HAVE_FDIP
+#cmakedefine HAVE_ZLIB
 #cmakedefine HAVE_GZBUFFER
 #cmakedefine HAVE_GDKPIXBUF
 #cmakedefine HAVE_LIBCCP4
diff --git a/libcrystfel/libcrystfel-config.h.meson.in b/libcrystfel/libcrystfel-config.h.meson.in
index ede17ab8..01f6940e 100644
--- a/libcrystfel/libcrystfel-config.h.meson.in
+++ b/libcrystfel/libcrystfel-config.h.meson.in
@@ -4,6 +4,7 @@
 #mesondefine HAVE_XGANDALF
 #mesondefine HAVE_PINKINDEXER
 #mesondefine HAVE_FDIP
+#mesondefine HAVE_ZLIB
 #mesondefine HAVE_GZBUFFER
 #mesondefine HAVE_LIBCCP4
 #mesondefine HAVE_MSGPACK
diff --git a/libcrystfel/meson.build b/libcrystfel/meson.build
index dc0fe2bf..b8dc4b6c 100644
--- a/libcrystfel/meson.build
+++ b/libcrystfel/meson.build
@@ -1,10 +1,13 @@
 # libcrystfel
 
-zlibdep = dependency('zlib', required: true)
-if cc.has_function('gzbuffer',
-                   prefix: '#include <zlib.h>',
-                   dependencies: zlibdep)
-  conf_data.set10('HAVE_GZBUFFER', 1)
+zlibdep = dependency('zlib', required: false)
+if zlibdep.found()
+  conf_data.set10('HAVE_ZLIB', 1)
+  if cc.has_function('gzbuffer',
+                     prefix: '#include <zlib.h>',
+                     dependencies: zlibdep)
+    conf_data.set10('HAVE_GZBUFFER', 1)
+  endif
 endif
 
 fftwdep = dependency('fftw3', required: false)
diff --git a/libcrystfel/src/image-cbf.c b/libcrystfel/src/image-cbf.c
index de9fc75a..51003934 100644
--- a/libcrystfel/src/image-cbf.c
+++ b/libcrystfel/src/image-cbf.c
@@ -32,9 +32,12 @@
 #include <assert.h>
 #include <math.h>
 #include <stdio.h>
-#include <zlib.h>
 #include <unistd.h>
 
+#ifdef HAVE_ZLIB
+#include <zlib.h>
+#endif
+
 #include "image.h"
 #include "utils.h"
 #include "detgeom.h"
@@ -284,6 +287,7 @@ static float *read_cbf_data(const char *filename, int gz, int *w, int *h)
 
 	} else {
 
+		#ifdef HAVE_ZLIB
 		gzFile gzfh;
 		int len_read;
 		size_t len;
@@ -293,8 +297,10 @@ static float *read_cbf_data(const char *filename, int gz, int *w, int *h)
 		gzfh = gzopen(filename, "rb");
 		if ( gzfh == NULL ) return NULL;
 
+		#ifdef HAVE_GZBUFFER
 		/* Set larger buffer size for hopefully faster uncompression */
 		gzbuffer(gzfh, 128*1024);
+		#endif
 
 		buf = malloc(bufsz);
 		if ( buf == NULL ) return NULL;
@@ -322,6 +328,10 @@ static float *read_cbf_data(const char *filename, int gz, int *w, int *h)
 
 		gzclose(gzfh);
 
+		#else
+		return NULL;
+		#endif
+
 	}
 
 	/* This is really horrible, but there are at least three different types
@@ -528,6 +538,7 @@ signed int is_cbf_file(const char *filename)
 
 signed int is_cbfgz_file(const char *filename)
 {
+	#ifdef HAVE_ZLIB
 	gzFile gzfh;
 	char line[1024];
 
@@ -541,6 +552,10 @@ signed int is_cbfgz_file(const char *filename)
 	}
 
 	return 1;
+
+	#else /* No zlib */
+	return 0;
+	#endif
 }