tor-browser

rescaler_utils.c (5945B)

---

// 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)

#include <assert.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>

#include "src/dsp/dsp.h"
#include "src/webp/types.h"
#include "src/utils/rescaler_utils.h"
#include "src/utils/utils.h"

//------------------------------------------------------------------------------

int 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) {
 const int x_add = src_width, x_sub = dst_width;
 const int y_add = src_height, y_sub = dst_height;
 const uint64_t total_size = 2ull * dst_width * num_channels * sizeof(*work);
 if (!CheckSizeOverflow(total_size)) return 0;

 rescaler->x_expand = (src_width < dst_width);
 rescaler->y_expand = (src_height < dst_height);
 rescaler->src_width = src_width;
 rescaler->src_height = src_height;
 rescaler->dst_width = dst_width;
 rescaler->dst_height = dst_height;
 rescaler->src_y = 0;
 rescaler->dst_y = 0;
 rescaler->dst = dst;
 rescaler->dst_stride = dst_stride;
 rescaler->num_channels = num_channels;

 // for 'x_expand', we use bilinear interpolation
 rescaler->x_add = rescaler->x_expand ? (x_sub - 1) : x_add;
 rescaler->x_sub = rescaler->x_expand ? (x_add - 1) : x_sub;
 if (!rescaler->x_expand) {  // fx_scale is not used otherwise
   rescaler->fx_scale = WEBP_RESCALER_FRAC(1, rescaler->x_sub);
 }
 // vertical scaling parameters
 rescaler->y_add = rescaler->y_expand ? y_add - 1 : y_add;
 rescaler->y_sub = rescaler->y_expand ? y_sub - 1 : y_sub;
 rescaler->y_accum = rescaler->y_expand ? rescaler->y_sub : rescaler->y_add;
 if (!rescaler->y_expand) {
   // This is WEBP_RESCALER_FRAC(dst_height, x_add * y_add) without the cast.
   // Its value is <= WEBP_RESCALER_ONE, because dst_height <= rescaler->y_add
   // and rescaler->x_add >= 1;
   const uint64_t num = (uint64_t)dst_height * WEBP_RESCALER_ONE;
   const uint64_t den = (uint64_t)rescaler->x_add * rescaler->y_add;
   const uint64_t ratio = num / den;
   if (ratio != (uint32_t)ratio) {
     // When ratio == WEBP_RESCALER_ONE, we can't represent the ratio with the
     // current fixed-point precision. This happens when src_height ==
     // rescaler->y_add (which == src_height), and rescaler->x_add == 1.
     // => We special-case fxy_scale = 0, in WebPRescalerExportRow().
     rescaler->fxy_scale = 0;
   } else {
     rescaler->fxy_scale = (uint32_t)ratio;
   }
   rescaler->fy_scale = WEBP_RESCALER_FRAC(1, rescaler->y_sub);
 } else {
   rescaler->fy_scale = WEBP_RESCALER_FRAC(1, rescaler->x_add);
   // rescaler->fxy_scale is unused here.
 }
 rescaler->irow = work;
 rescaler->frow = work + num_channels * dst_width;
 memset(work, 0, (size_t)total_size);

 WebPRescalerDspInit();
 return 1;
}

int WebPRescalerGetScaledDimensions(int src_width, int src_height,
                                   int* const scaled_width,
                                   int* const scaled_height) {
 assert(scaled_width != NULL);
 assert(scaled_height != NULL);
 {
   int width = *scaled_width;
   int height = *scaled_height;
   const int max_size = INT_MAX / 2;

   // if width is unspecified, scale original proportionally to height ratio.
   if (width == 0 && src_height > 0) {
     width =
         (int)(((uint64_t)src_width * height + src_height - 1) / src_height);
   }
   // if height is unspecified, scale original proportionally to width ratio.
   if (height == 0 && src_width > 0) {
     height =
         (int)(((uint64_t)src_height * width + src_width - 1) / src_width);
   }
   // Check if the overall dimensions still make sense.
   if (width <= 0 || height <= 0 || width > max_size || height > max_size) {
     return 0;
   }

   *scaled_width = width;
   *scaled_height = height;
   return 1;
 }
}

//------------------------------------------------------------------------------
// all-in-one calls

int WebPRescaleNeededLines(const WebPRescaler* const rescaler,
                          int max_num_lines) {
 const int num_lines =
     (rescaler->y_accum + rescaler->y_sub - 1) / rescaler->y_sub;
 return (num_lines > max_num_lines) ? max_num_lines : num_lines;
}

int WebPRescalerImport(WebPRescaler* const rescaler, int num_lines,
                      const uint8_t* src, int src_stride) {
 int total_imported = 0;
 while (total_imported < num_lines &&
        !WebPRescalerHasPendingOutput(rescaler)) {
   if (rescaler->y_expand) {
     rescaler_t* const tmp = rescaler->irow;
     rescaler->irow = rescaler->frow;
     rescaler->frow = tmp;
   }
   WebPRescalerImportRow(rescaler, src);
   if (!rescaler->y_expand) {    // Accumulate the contribution of the new row.
     int x;
     for (x = 0; x < rescaler->num_channels * rescaler->dst_width; ++x) {
       rescaler->irow[x] += rescaler->frow[x];
     }
   }
   ++rescaler->src_y;
   src += src_stride;
   ++total_imported;
   rescaler->y_accum -= rescaler->y_sub;
 }
 return total_imported;
}

int WebPRescalerExport(WebPRescaler* const rescaler) {
 int total_exported = 0;
 while (WebPRescalerHasPendingOutput(rescaler)) {
   WebPRescalerExportRow(rescaler);
   ++total_exported;
 }
 return total_exported;
}

//------------------------------------------------------------------------------