core: Add video dumper interface

The VideoFrame is rotated while copying, to put the pixels in their correct positions (OpenGL seems to return the image in reverted order by default)

src/core/dumping/backend.cpp

@@ -0,0 +1,26 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <cstring>
+#include "core/dumping/backend.h"
+
+namespace VideoDumper {
+
+VideoFrame::VideoFrame(std::size_t width_, std::size_t height_, u8* data_)
+    : width(width_), height(height_), stride(width * 4), data(width * height * 4) {
+    // While copying, rotate the image to put the pixels in correct order
+    // (As OpenGL returns pixel data starting from the lowest position)
+    for (std::size_t i = 0; i < height; i++) {
+        for (std::size_t j = 0; j < width; j++) {
+            for (std::size_t k = 0; k < 4; k++) {
+                data[i * stride + j * 4 + k] = data_[(height - i - 1) * stride + j * 4 + k];
+            }
+        }
+    }
+}
+
+Backend::~Backend() = default;
+NullBackend::~NullBackend() = default;
+
+} // namespace VideoDumper