// Given previous and current canvas, picks the optimal rectangle for the
// current frame. The initial guess for 'rect' will be the full canvas.
static int GetSubRect(const WebPPicture* const prev_canvas,
const WebPPicture* const curr_canvas, int is_key_frame,
int is_first_frame, int empty_rect_allowed,
FrameRect* const rect, WebPPicture* const sub_frame) {
rect->x_offset_ = 0;
rect->y_offset_ = 0;
rect->width_ = curr_canvas->width;
rect->height_ = curr_canvas->height;
if (!is_key_frame || is_first_frame) { // Optimize frame rectangle.
// Note: This behaves as expected for first frame, as 'prev_canvas' is
// initialized to a fully transparent canvas in the beginning.
MinimizeChangeRectangle(prev_canvas, curr_canvas, rect);
}
if (IsEmptyRect(rect)) {
if (empty_rect_allowed) { // No need to get 'sub_frame'.
return 1;
} else { // Force a 1x1 rectangle.
rect->width_ = 1;
rect->height_ = 1;
assert(rect->x_offset_ == 0);
assert(rect->y_offset_ == 0);
}
}
SnapToEvenOffsets(rect);
return WebPPictureView(curr_canvas, rect->x_offset_, rect->y_offset_,
rect->width_, rect->height_, sub_frame);
}
// Given previous and current canvas, picks the optimal rectangle for the
// current frame. The initial guess for 'rect' will be the full canvas.
static int GetSubRect(const WebPPicture* const prev_canvas,
const WebPPicture* const curr_canvas, int is_key_frame,
int is_first_frame, FrameRect* const rect,
WebPPicture* const sub_frame) {
rect->x_offset_ = 0;
rect->y_offset_ = 0;
rect->width_ = curr_canvas->width;
rect->height_ = curr_canvas->height;
if (!is_key_frame || is_first_frame) { // Optimize frame rectangle.
// Note: This behaves as expected for first frame, as 'prev_canvas' is
// initialized to a fully transparent canvas in the beginning.
MinimizeChangeRectangle(prev_canvas, curr_canvas, rect);
}
SnapToEvenOffsets(rect);
return WebPPictureView(curr_canvas, rect->x_offset_, rect->y_offset_,
rect->width_, rect->height_, sub_frame);
}
