VP8StatusCode WebPAllocateDecBuffer(int w, int h, WebPDecoderOptions options, WebPDecBuffer _out)
{
if (_out == null || w <= 0 || h <= 0) {
return VP8_STATUS_INVALID_PARAM;
}
if (options != null) { // First, apply options if there is any.
if (options.use_cropping) {
int cw = options.crop_width;
int ch = options.crop_height;
int x = options.crop_left & ~1;
int y = options.crop_top & ~1;
if (x < 0 || y < 0 || cw <= 0 || ch <= 0 || x + cw > w || y + ch > h) {
return VP8_STATUS_INVALID_PARAM; // out of frame boundary.
}
w = cw;
h = ch;
}
if (options.use_scaling) {
if (options.scaled_width <= 0 || options.scaled_height <= 0) {
return VP8_STATUS_INVALID_PARAM;
}
w = options.scaled_width;
h = options.scaled_height;
}
}
_out.width = w;
_out.height = h;
// Then, allocate buffer for real
return _out.AllocateBuffer();
}
//------------------------------------------------------------------------------
// Default custom functions
// Setup crop_xxx fields, mb_w and mb_h
static int InitFromOptions(WebPDecoderOptions* options,
VP8Io* io) {
int W = io.width;
int H = io.height;
int x = 0, y = 0, w = W, h = H;
// Cropping
io.use_cropping = (options != null) && (options.use_cropping > 0);
if (io.use_cropping) {
w = options.crop_width;
h = options.crop_height;
// TODO(skal): take colorspace into account. Don't assume YUV420.
x = options.crop_left & ~1;
y = options.crop_top & ~1;
if (x < 0 || y < 0 || w <= 0 || h <= 0 || x + w > W || y + h > H) {
return 0; // out of frame boundary error
}
}
io.crop_left = x;
io.crop_top = y;
io.crop_right = x + w;
io.crop_bottom = y + h;
io.mb_w = w;
io.mb_h = h;
// Scaling
io.use_scaling = (options != null) && (options.use_scaling > 0);
if (io.use_scaling) {
if (options.scaled_width <= 0 || options.scaled_height <= 0) {
return 0;
}
io.scaled_width = options.scaled_width;
io.scaled_height = options.scaled_height;
}
// Filter
io.bypass_filtering = options && options.bypass_filtering;
// Fancy upsampler
#if FANCY_UPSAMPLING
io.fancy_upsampling = (options == null) || (!options.no_fancy_upsampling);
#endif
if (io.use_scaling) {
// disable filter (only for large downscaling ratio).
io.bypass_filtering = (io.scaled_width < W * 3 / 4) &&
(io.scaled_height < H * 3 / 4);
io.fancy_upsampling = 0;
}
return 1;
}
