Fix #109: XBM reading fails with printed error

When calculating the number of required bytes of an XBM image, we have
to take the line padding into account.

src/gd_xbm.c

@@ -108,7 +108,7 @@ BGD_DECLARE(gdImagePtr) gdImageCreateFromXbm(FILE * fd)
 				max_bit = 32768;
 			}
 			if (max_bit) {
-				bytes = (width * height / 8) + 1;
+                bytes = (width + 7) / 8 * height;
 				if (!bytes) {
 					return 0;
 				}

tests/xbm/.gitignore

@@ -1 +1,2 @@
+/github_bug_109
 /github_bug_170

tests/xbm/CMakeLists.txt

@@ -1,4 +1,5 @@
 LIST(APPEND TESTS_FILES
+	github_bug_109
 	github_bug_170
 )
 

tests/xbm/Makemodule.am

@@ -1,5 +1,8 @@
 libgd_test_programs += \
+	xbm/github_bug_109 \
 	xbm/github_bug_170
 
 EXTRA_DIST += \
-	xbm/CMakeLists.txt
+	xbm/CMakeLists.txt \
+	xbm/github_bug_109.xbm \
+	xbm/github_bug_109_exp.png

tests/xbm/github_bug_109.c

@@ -0,0 +1,35 @@
+/**
+ * Test reading of XBM images with a width that is not a multiple of 8
+ *
+ * We're reading such an XBM image, and check that we got what we've expected,
+ * instead of an error message.
+ *
+ * See also <https://github.com/libgd/libgd/issues/109>.
+ */
+
+
+#include "gd.h"
+#include "gdtest.h"
+
+
+int main()
+{
+    gdImagePtr im;
+    FILE *fp;
+    char *path;
+
+    fp = gdTestFileOpen2("xbm", "github_bug_109.xbm");
+    im = gdImageCreateFromXbm(fp);
+    fclose(fp);
+    gdTestAssert(im != NULL);
+    gdTestAssert(gdImageGetTrueColorPixel(im, 0, 0) == 0);
+    gdTestAssert(gdImageGetTrueColorPixel(im, 0, 1) == 0xffffff);
+
+    path = gdTestFilePath2("xbm", "github_bug_109_exp.png");
+    gdAssertImageEqualsToFile(path, im);
+    gdFree(path);
+
+    gdImageDestroy(im);
+
+    return gdNumFailures();
+}

tests/xbm/github_bug_109.xbm

@@ -0,0 +1,5 @@
+#define test_width 10
+#define test_height 10
+static unsigned char test_bits[] = {
+  0xFF, 0x03, 0x00, 0x00, 0xFF, 0x03, 0x00, 0x00, 0xFF, 0x03, 0x00, 0x00, 
+  0xFF, 0x03, 0x00, 0x00, 0xFF, 0x03, 0x00, 0x00};