diff --git a/lib/convert.ts b/lib/convert.ts
index b47b0c0..1c3a4cc 100644
--- a/lib/convert.ts
+++ b/lib/convert.ts
@@ -225,10 +225,8 @@ const lv_image_dsc_t ${out_name} = {
     }
 
     classify_pixel(value, bits) {
-      const tmp = 1 << (8 - bits);
-      let val = Math.round(value / tmp) * tmp;
-      if(val < 0) val = 0;
-      return val;
+        const shift = 8 - bits;
+        return value >> shift << shift;
     }
 
     format_to_c_array() {