diff --git a/src/gfx/process.cpp b/src/gfx/process.cpp
index cfab0a5b..270e2a2e 100644
--- a/src/gfx/process.cpp
+++ b/src/gfx/process.cpp
@@ -179,8 +179,13 @@ struct Image {
 		std::unordered_set<std::pair<uint32_t, uint32_t>, decltype(hashPair)> fusions;
 
 		// Register colors from `png` into `colors`
-		for (uint32_t y = 0; y < png.height; ++y) {
-			for (uint32_t x = 0; x < png.width; ++x) {
+		uint32_t const pxLeft = options.inputSlice.width ? options.inputSlice.left : 0;
+		uint32_t const pxTop = options.inputSlice.height ? options.inputSlice.top : 0;
+		uint32_t const pxRight = options.inputSlice.width ? options.inputSlice.right() : png.width;
+		uint32_t const pxBottom =
+		    options.inputSlice.height ? options.inputSlice.bottom() : png.height;
+		for (uint32_t y = pxTop; y < pxBottom; ++y) {
+			for (uint32_t x = pxLeft; x < pxRight; ++x) {
 				if (Rgba const &color = pixel(x, y); color.isAmbiguous()) {
 					// Report ambiguously transparent or opaque colors
 					if (uint32_t css = color.toCSS(); ambiguous.find(css) == ambiguous.end()) {
diff --git a/test/gfx/trans_outside_slice.flags b/test/gfx/trans_outside_slice.flags
new file mode 100644
index 00000000..d26d028a
--- /dev/null
+++ b/test/gfx/trans_outside_slice.flags
@@ -0,0 +1 @@
+-L 8,8:1,1
diff --git a/test/gfx/trans_outside_slice.out.2bpp b/test/gfx/trans_outside_slice.out.2bpp
new file mode 100644
index 00000000..920ab83e
--- /dev/null
+++ b/test/gfx/trans_outside_slice.out.2bpp
@@ -0,0 +1 @@
+<Ì<Ì<Ì<Ì<Ì<Ì<Ì<Ì
\ No newline at end of file
diff --git a/test/gfx/trans_outside_slice.out.attrmap b/test/gfx/trans_outside_slice.out.attrmap
new file mode 100644
index 00000000..f76dd238
Binary files /dev/null and b/test/gfx/trans_outside_slice.out.attrmap differ
diff --git a/test/gfx/trans_outside_slice.out.pal b/test/gfx/trans_outside_slice.out.pal
new file mode 100644
index 00000000..8d370931
Binary files /dev/null and b/test/gfx/trans_outside_slice.out.pal differ
diff --git a/test/gfx/trans_outside_slice.out.tilemap b/test/gfx/trans_outside_slice.out.tilemap
new file mode 100644
index 00000000..f76dd238
Binary files /dev/null and b/test/gfx/trans_outside_slice.out.tilemap differ
diff --git a/test/gfx/trans_outside_slice.png b/test/gfx/trans_outside_slice.png
new file mode 100644
index 00000000..567a5033
Binary files /dev/null and b/test/gfx/trans_outside_slice.png differ