Notes on Microsoft Desktop Duplication API

Introduction

Desktop Duplication API gives apps frame-by-frame access to the desktop image via DXGO surfaces, so you can throw GPU processing at each frame update.

Getting Frames

Call IDXGIOutputDuplication::AcquireNextFrame to get the current desktop as a DXGI surface. Format is always DXGI_FORMAT_B8G8R8A8_UNORM regardless of display mode.

Knowing what changed

Two methods tell you which pixels actually needed processing:

1. GetFrameDirtyRects: returns non-overlapping rectangles covering areas the OS repainted since your last frame.
2. GetFrameMoveRects: returns regions the OS moved within the same image (e.g. scrolling). Each entry has a source point and destination rect. Always same size, no stretching.

The pattern: dirty rects = repainted pixels, move rects = relocated pixels. Process move regions first (they reference old frame data), then dirty rects.