[core] Clear atlasImage rect for a removed pattern

1 files changed, 26 insertions, 0 deletions

diff --git a/include/mbgl/util/image.hpp b/include/mbgl/util/image.hpp
index cb28f3da8d..4887058f79 100644
--- a/include/mbgl/util/image.hpp
+++ b/include/mbgl/util/image.hpp
@@ -5,6 +5,7 @@
 #include <mbgl/util/size.hpp>
 
 #include <string>
+#include <cstring>
 #include <memory>
 #include <algorithm>
 
@@ -91,6 +92,31 @@ public:
         operator=(std::move(newImage));
     }
 
+    // Clears the rect area specified by `pt` and `size` from `dstImage`.
+    static void clear(Image& dstImg, const Point<uint32_t>& pt, const Size& size) {
+        if (size.isEmpty()) {
+            return;
+        }
+
+        if (!dstImg.valid()) {
+            throw std::invalid_argument("invalid destination for image clear");
+        }
+
+        if (size.width > dstImg.size.width ||
+            size.height > dstImg.size.height ||
+            pt.x > dstImg.size.width - size.width ||
+            pt.y > dstImg.size.height - size.height) {
+            throw std::out_of_range("out of range destination coordinates for image clear");
+        }
+
+        uint8_t* dstData = dstImg.data.get();
+
+        for (uint32_t y = 0; y < size.height; y++) {
+            const std::size_t dstOffset = (pt.y + y) * dstImg.stride() + pt.x * channels;
+            std::memset(dstData + dstOffset, 0, size.width * channels);
+        }
+    }
+
     // Copy image data within `rect` from `src` to the rectangle of the same size at `pt`
     // in `dst`. If the specified bounds exceed the bounds of the source or destination,
     // throw `std::out_of_range`. Must not be used to move data within a single Image.