Backported of:

From 3e52dabe3e64dc50f4422effe364a1457a8a8592 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Sat, 29 Dec 2018 22:35:07 +0100
Subject: [PATCH] img2txt: fix an integer overflow in the BMP loader.

Fixes: #37 (CVE-2018-20545)
Fixes: #40 (CVE-2018-20548)
Fixes: #41 (CVE-2018-20549)
diff --git a/src/common-image.h b/src/common-image.h
index efc6069..1b99302 100644
--- a/src/common-image.h
+++ b/src/common-image.h
@@ -13,7 +13,7 @@
 struct image
 {
     char *pixels;
-    unsigned int w, h;
+    size_t w, h;
     struct caca_dither *dither;
     void *priv;
 };