Scanline decoding for bmp

src/codec/SkCodecPriv.h

Index: src/codec/SkCodecPriv.h
diff --git a/src/codec/SkCodecPriv.h b/src/codec/SkCodecPriv.h
index 450457f630137c98b854be9f2ad8ad963f8c71d0..5f4b5651996bc0f9392a5f952722da75a968cadf 100644
--- a/src/codec/SkCodecPriv.h
+++ b/src/codec/SkCodecPriv.h
@@ -131,6 +131,16 @@ static inline size_t compute_row_bytes(int width, uint32_t bitsPerPixel) {
     }
 }
 
+static bool is_coord_necessary(int srcCoord, int start, int sampleSize, int scaledDim) {
+    // Check for edge cases on the first few rows or the last few rows
+    if (srcCoord < start || srcCoord / sampleSize >= scaledDim) {
+        return false;
+    }
+
+    // Every sampleY rows are necessary
+    return ((srcCoord - start) % sampleSize) == 0;
+}
+
 /*
  * Get a byte from a buffer
  * This method is unsafe, the caller is responsible for performing a check