diff options
Diffstat (limited to 'drivers/webpold/dec/alpha.c')
| -rw-r--r-- | drivers/webpold/dec/alpha.c | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/drivers/webpold/dec/alpha.c b/drivers/webpold/dec/alpha.c new file mode 100644 index 0000000000..d1095fa555 --- /dev/null +++ b/drivers/webpold/dec/alpha.c @@ -0,0 +1,140 @@ +// Copyright 2011 Google Inc. All Rights Reserved. +// +// This code is licensed under the same terms as WebM: +// Software License Agreement: http://www.webmproject.org/license/software/ +// Additional IP Rights Grant: http://www.webmproject.org/license/additional/ +// ----------------------------------------------------------------------------- +// +// Alpha-plane decompression. +// +// Author: Skal (pascal.massimino@gmail.com) + +#include <stdlib.h> +#include "./vp8i.h" +#include "./vp8li.h" +#include "../utils/filters.h" +#include "../utils/quant_levels.h" +#include "../format_constants.h" + +#if defined(__cplusplus) || defined(c_plusplus) +extern "C" { +#endif + +// TODO(skal): move to dsp/ ? +static void CopyPlane(const uint8_t* src, int src_stride, + uint8_t* dst, int dst_stride, int width, int height) { + while (height-- > 0) { + memcpy(dst, src, width); + src += src_stride; + dst += dst_stride; + } +} + +//------------------------------------------------------------------------------ +// Decodes the compressed data 'data' of size 'data_size' into the 'output'. +// The 'output' buffer should be pre-allocated and must be of the same +// dimension 'height'x'stride', as that of the image. +// +// Returns 1 on successfully decoding the compressed alpha and +// 0 if either: +// error in bit-stream header (invalid compression mode or filter), or +// error returned by appropriate compression method. + +static int DecodeAlpha(const uint8_t* data, size_t data_size, + int width, int height, int stride, uint8_t* output) { + uint8_t* decoded_data = NULL; + const size_t decoded_size = height * width; + uint8_t* unfiltered_data = NULL; + WEBP_FILTER_TYPE filter; + int pre_processing; + int rsrv; + int ok = 0; + int method; + + assert(width > 0 && height > 0 && stride >= width); + assert(data != NULL && output != NULL); + + if (data_size <= ALPHA_HEADER_LEN) { + return 0; + } + + method = (data[0] >> 0) & 0x03; + filter = (data[0] >> 2) & 0x03; + pre_processing = (data[0] >> 4) & 0x03; + rsrv = (data[0] >> 6) & 0x03; + if (method < ALPHA_NO_COMPRESSION || + method > ALPHA_LOSSLESS_COMPRESSION || + filter >= WEBP_FILTER_LAST || + pre_processing > ALPHA_PREPROCESSED_LEVELS || + rsrv != 0) { + return 0; + } + + if (method == ALPHA_NO_COMPRESSION) { + ok = (data_size >= decoded_size); + decoded_data = (uint8_t*)data + ALPHA_HEADER_LEN; + } else { + decoded_data = (uint8_t*)malloc(decoded_size); + if (decoded_data == NULL) return 0; + ok = VP8LDecodeAlphaImageStream(width, height, + data + ALPHA_HEADER_LEN, + data_size - ALPHA_HEADER_LEN, + decoded_data); + } + + if (ok) { + WebPFilterFunc unfilter_func = WebPUnfilters[filter]; + if (unfilter_func != NULL) { + unfiltered_data = (uint8_t*)malloc(decoded_size); + if (unfiltered_data == NULL) { + ok = 0; + goto Error; + } + // TODO(vikas): Implement on-the-fly decoding & filter mechanism to decode + // and apply filter per image-row. + unfilter_func(decoded_data, width, height, 1, width, unfiltered_data); + // Construct raw_data (height x stride) from alpha data (height x width). + CopyPlane(unfiltered_data, width, output, stride, width, height); + free(unfiltered_data); + } else { + // Construct raw_data (height x stride) from alpha data (height x width). + CopyPlane(decoded_data, width, output, stride, width, height); + } + if (pre_processing == ALPHA_PREPROCESSED_LEVELS) { + ok = DequantizeLevels(decoded_data, width, height); + } + } + + Error: + if (method != ALPHA_NO_COMPRESSION) { + free(decoded_data); + } + return ok; +} + +//------------------------------------------------------------------------------ + +const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec, + int row, int num_rows) { + const int stride = dec->pic_hdr_.width_; + + if (row < 0 || num_rows < 0 || row + num_rows > dec->pic_hdr_.height_) { + return NULL; // sanity check. + } + + if (row == 0) { + // Decode everything during the first call. + if (!DecodeAlpha(dec->alpha_data_, (size_t)dec->alpha_data_size_, + dec->pic_hdr_.width_, dec->pic_hdr_.height_, stride, + dec->alpha_plane_)) { + return NULL; // Error. + } + } + + // Return a pointer to the current decoded row. + return dec->alpha_plane_ + row * stride; +} + +#if defined(__cplusplus) || defined(c_plusplus) +} // extern "C" +#endif |