libwebp-0.6.0-rc1

third_party/libwebp/utils/rescaler.h

-// Copyright 2012 Google Inc. All Rights Reserved.
-//
-// Use of this source code is governed by a BSD-style license
-// that can be found in the COPYING file in the root of the source
-// tree. An additional intellectual property rights grant can be found
-// in the file PATENTS. All contributing project authors may
-// be found in the AUTHORS file in the root of the source tree.
-// -----------------------------------------------------------------------------
-//
-// Rescaling functions
-//
-// Author: Skal (pascal.massimino@gmail.com)
-
-#ifndef WEBP_UTILS_RESCALER_H_
-#define WEBP_UTILS_RESCALER_H_
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#include "../webp/types.h"
-
-#define WEBP_RESCALER_RFIX 32   // fixed-point precision for multiplies
-#define WEBP_RESCALER_ONE (1ull << WEBP_RESCALER_RFIX)
-#define WEBP_RESCALER_FRAC(x, y) \
-    ((uint32_t)(((uint64_t)(x) << WEBP_RESCALER_RFIX) / (y)))
-
-// Structure used for on-the-fly rescaling
-typedef uint32_t rescaler_t;   // type for side-buffer
-typedef struct WebPRescaler WebPRescaler;
-struct WebPRescaler {
-  int x_expand;               // true if we're expanding in the x direction
-  int y_expand;               // true if we're expanding in the y direction
-  int num_channels;           // bytes to jump between pixels
-  uint32_t fx_scale;          // fixed-point scaling factors
-  uint32_t fy_scale;          // ''
-  uint32_t fxy_scale;         // ''
-  int y_accum;                // vertical accumulator
-  int y_add, y_sub;           // vertical increments
-  int x_add, x_sub;           // horizontal increments
-  int src_width, src_height;  // source dimensions
-  int dst_width, dst_height;  // destination dimensions
-  int src_y, dst_y;           // row counters for input and output
-  uint8_t* dst;
-  int dst_stride;
-  rescaler_t* irow, *frow;    // work buffer
-};
-
-// Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
-void WebPRescalerInit(WebPRescaler* const rescaler,
-                      int src_width, int src_height,
-                      uint8_t* const dst,
-                      int dst_width, int dst_height, int dst_stride,
-                      int num_channels,
-                      rescaler_t* const work);
-
-// If either 'scaled_width' or 'scaled_height' (but not both) is 0 the value
-// will be calculated preserving the aspect ratio, otherwise the values are
-// left unmodified. Returns true on success, false if either value is 0 after
-// performing the scaling calculation.
-int WebPRescalerGetScaledDimensions(int src_width, int src_height,
-                                    int* const scaled_width,
-                                    int* const scaled_height);
-
-// Returns the number of input lines needed next to produce one output line,
-// considering that the maximum available input lines are 'max_num_lines'.
-int WebPRescaleNeededLines(const WebPRescaler* const rescaler,
-                           int max_num_lines);
-
-// Import multiple rows over all channels, until at least one row is ready to
-// be exported. Returns the actual number of lines that were imported.
-int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
-                       const uint8_t* src, int src_stride);
-
-// Export as many rows as possible. Return the numbers of rows written.
-int WebPRescalerExport(WebPRescaler* const rescaler);
-
-// Return true if input is finished
-static WEBP_INLINE
-int WebPRescalerInputDone(const WebPRescaler* const rescaler) {
-  return (rescaler->src_y >= rescaler->src_height);
-}
-// Return true if output is finished
-static WEBP_INLINE
-int WebPRescalerOutputDone(const WebPRescaler* const rescaler) {
-  return (rescaler->dst_y >= rescaler->dst_height);
-}
-
-// Return true if there are pending output rows ready.
-static WEBP_INLINE
-int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
-  return !WebPRescalerOutputDone(rescaler) && (rescaler->y_accum <= 0);
-}
-
-//------------------------------------------------------------------------------
-
-#ifdef __cplusplus
-}    // extern "C"
-#endif
-
-#endif  /* WEBP_UTILS_RESCALER_H_ */