diff --git a/firmware/src/tools/conv.c b/firmware/src/tools/conv.c
new file mode 100644
index 0000000..718648e
--- /dev/null
+++ b/firmware/src/tools/conv.c
@@ -0,0 +1,95 @@
+/*
+ * Image compression tool (zero-run-length encoding)
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include "bg_anima_8b.h"
+
+
+static int col = 0;
+
+static void line_begin()
+{
+    col = 0;
+}
+
+static void out_byte(uint8_t byte)
+{
+    if (col == 0) {
+        printf("\n   ");
+        col == 0;
+    }
+    printf(" 0x%02x,", byte);
+    col = (col + 1) % 16;
+}
+
+static int zero_count = 0;
+
+static int out_zero()
+{
+    if (!zero_count) {
+        return 0;
+    }
+
+    out_byte(0);
+    out_byte(zero_count);
+    zero_count = 0;
+
+    return 2;
+}
+
+static int encode_byte(uint8_t byte, bool end)
+{
+    if (byte == 0) {
+        zero_count++;
+    }
+
+    int written = 0;
+    
+    if ((byte != 0) || (zero_count == 255) || end) {
+        written += out_zero();
+    }
+
+    if (byte != 0) {
+        out_byte(byte);
+        written++;
+    }
+
+    return written;
+}
+    
+static int out_frame(int frame, int frame_size)
+{
+    const uint8_t *frame_data = stars_gif.data + frame * frame_size;
+    printf("\n    // frame %d", frame);
+    line_begin();
+    int written = 0;
+    for (int i = 0; i < frame_size - 1; i++) {
+        written += encode_byte(frame_data[i], false);
+    }
+    written += encode_byte(frame_data[frame_size - 1], true);
+    return written;
+}
+
+
+int main()
+{
+    int frame_index[stars_gif.frames];
+
+    printf("const uint8_t data[] = {");
+    int sum = 0;
+    for (int frame = 0; frame < stars_gif.frames; frame++) {
+        frame_index[frame] = sum;
+        sum += out_frame(frame, stars_gif.width * stars_gif.height);
+    }
+    printf("\n};\n");
+
+    printf("const uint32_t index[] = {\n   ");
+    for (int frame = 0; frame < stars_gif.frames; frame++) {
+        printf(" %d,", frame_index[frame]);
+    }
+    printf("\n};\n");
+    printf("Total: %d\n", sum);
+}
\ No newline at end of file