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      1 // Copyright 2012 Google Inc. All Rights Reserved.
      2 //
      3 // This code is licensed under the same terms as WebM:
      4 //  Software License Agreement:  http://www.webmproject.org/license/software/
      5 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
      6 // -----------------------------------------------------------------------------
      7 //
      8 // Image transforms and color space conversion methods for lossless decoder.
      9 //
     10 // Authors: Vikas Arora (vikaas.arora (at) gmail.com)
     11 //          Jyrki Alakuijala (jyrki (at) google.com)
     12 
     13 #ifndef WEBP_DSP_LOSSLESS_H_
     14 #define WEBP_DSP_LOSSLESS_H_
     15 
     16 #include "webp/types.h"
     17 #include "webp/decode.h"
     18 
     19 #if defined(__cplusplus) || defined(c_plusplus)
     20 extern "C" {
     21 #endif
     22 
     23 //------------------------------------------------------------------------------
     24 // Image transforms.
     25 
     26 struct VP8LTransform;  // Defined in dec/vp8li.h.
     27 
     28 // Performs inverse transform of data given transform information, start and end
     29 // rows. Transform will be applied to rows [row_start, row_end[.
     30 // The *in and *out pointers refer to source and destination data respectively
     31 // corresponding to the intermediate row (row_start).
     32 void VP8LInverseTransform(const struct VP8LTransform* const transform,
     33                           int row_start, int row_end,
     34                           const uint32_t* const in, uint32_t* const out);
     35 
     36 // Subtracts green from blue and red channels.
     37 void VP8LSubtractGreenFromBlueAndRed(uint32_t* argb_data, int num_pixs);
     38 
     39 void VP8LResidualImage(int width, int height, int bits,
     40                        uint32_t* const argb, uint32_t* const argb_scratch,
     41                        uint32_t* const image);
     42 
     43 void VP8LColorSpaceTransform(int width, int height, int bits, int step,
     44                              uint32_t* const argb, uint32_t* image);
     45 
     46 //------------------------------------------------------------------------------
     47 // Color space conversion.
     48 
     49 // Converts from BGRA to other color spaces.
     50 void VP8LConvertFromBGRA(const uint32_t* const in_data, int num_pixels,
     51                          WEBP_CSP_MODE out_colorspace, uint8_t* const rgba);
     52 
     53 //------------------------------------------------------------------------------
     54 // Misc methods.
     55 
     56 // Computes sampled size of 'size' when sampling using 'sampling bits'.
     57 static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
     58                                               uint32_t sampling_bits) {
     59   return (size + (1 << sampling_bits) - 1) >> sampling_bits;
     60 }
     61 
     62 // Faster logarithm for integers, with the property of log2(0) == 0.
     63 float VP8LFastLog2(int v);
     64 // Fast calculation of v * log2(v) for integer input.
     65 static WEBP_INLINE float VP8LFastSLog2(int v) { return VP8LFastLog2(v) * v; }
     66 
     67 // In-place difference of each component with mod 256.
     68 static WEBP_INLINE uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
     69   const uint32_t alpha_and_green =
     70       0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);
     71   const uint32_t red_and_blue =
     72       0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);
     73   return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
     74 }
     75 
     76 //------------------------------------------------------------------------------
     77 
     78 #if defined(__cplusplus) || defined(c_plusplus)
     79 }    // extern "C"
     80 #endif
     81 
     82 #endif  // WEBP_DSP_LOSSLESS_H_
     83