go-libwebp

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;
 }
 
 //------------------------------------------------------------------------------