libwebp: update to 0.5.0

third_party/libwebp/utils/rescaler.c

 // 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 <stdlib.h>
 #include <string.h>
+#include "../dsp/dsp.h"
 #include "./rescaler.h"
-#include "../dsp/dsp.h"
-
-//------------------------------------------------------------------------------
-// Implementations of critical functions ImportRow / ExportRow
-
-// Import a row of data and save its contribution in the rescaler.
-// 'channel' denotes the channel number to be imported. 'Expand' corresponds to
-// the wrk->x_expand case. Otherwise, 'Shrink' is to be used.
-typedef void (*WebPRescalerImportRowFunc)(WebPRescaler* const wrk,
-                                          const uint8_t* src);
-static WebPRescalerImportRowFunc WebPRescalerImportRowExpand;
-static WebPRescalerImportRowFunc WebPRescalerImportRowShrink;
-
-// Export one row (starting at x_out position) from rescaler.
-// 'Expand' corresponds to the wrk->y_expand case.
-// Otherwise 'Shrink' is to be used
-typedef void (*WebPRescalerExportRowFunc)(WebPRescaler* const wrk);
-static WebPRescalerExportRowFunc WebPRescalerExportRowExpand;
-static WebPRescalerExportRowFunc WebPRescalerExportRowShrink;
-
-#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)))
-#define ROUNDER (WEBP_RESCALER_ONE >> 1)
-#define MULT_FIX(x, y) (((uint64_t)(x) * (y) + ROUNDER) >> WEBP_RESCALER_RFIX)
-
-static void ImportRowExpandC(WebPRescaler* const wrk, const uint8_t* src) {
-  const int x_stride = wrk->num_channels;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  int channel;
-  assert(!WebPRescalerInputDone(wrk));
-  assert(wrk->x_expand);
-  for (channel = 0; channel < x_stride; ++channel) {
-    int x_in = channel;
-    int x_out = channel;
-    // simple bilinear interpolation
-    int accum = wrk->x_add;
-    int left = src[x_in];
-    int right = (wrk->src_width > 1) ? src[x_in + x_stride] : left;
-    x_in += x_stride;
-    while (1) {
-      wrk->frow[x_out] = right * wrk->x_add + (left - right) * accum;
-      x_out += x_stride;
-      if (x_out >= x_out_max) break;
-      accum -= wrk->x_sub;
-      if (accum < 0) {
-        left = right;
-        x_in += x_stride;
-        assert(x_in < wrk->src_width * x_stride);
-        right = src[x_in];
-        accum += wrk->x_add;
-      }
-    }
-    assert(wrk->x_sub == 0 /* <- special case for src_width=1 */ || accum == 0);
-  }
-}
-
-static void ImportRowShrinkC(WebPRescaler* const wrk, const uint8_t* src) {
-  const int x_stride = wrk->num_channels;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  int channel;
-  assert(!WebPRescalerInputDone(wrk));
-  assert(!wrk->x_expand);
-  for (channel = 0; channel < x_stride; ++channel) {
-    int x_in = channel;
-    int x_out = channel;
-    uint32_t sum = 0;
-    int accum = 0;
-    while (x_out < x_out_max) {
-      uint32_t base = 0;
-      accum += wrk->x_add;
-      while (accum > 0) {
-        accum -= wrk->x_sub;
-        assert(x_in < wrk->src_width * x_stride);
-        base = src[x_in];
-        sum += base;
-        x_in += x_stride;
-      }
-      {        // Emit next horizontal pixel.
-        const rescaler_t frac = base * (-accum);
-        wrk->frow[x_out] = sum * wrk->x_sub - frac;
-        // fresh fractional start for next pixel
-        sum = (int)MULT_FIX(frac, wrk->fx_scale);
-      }
-      x_out += x_stride;
-    }
-    assert(accum == 0);
-  }
-}
-
-//------------------------------------------------------------------------------
-// Row export
-
-static void ExportRowExpandC(WebPRescaler* const wrk) {
-  int x_out;
-  uint8_t* const dst = wrk->dst;
-  rescaler_t* const irow = wrk->irow;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  const rescaler_t* const frow = wrk->frow;
-  assert(!WebPRescalerOutputDone(wrk));
-  assert(wrk->y_accum <= 0);
-  assert(wrk->y_expand);
-  assert(wrk->y_sub != 0);
-  if (wrk->y_accum == 0) {
-    for (x_out = 0; x_out < x_out_max; ++x_out) {
-      const uint32_t J = frow[x_out];
-      const int v = (int)MULT_FIX(J, wrk->fy_scale);
-      assert(v >= 0 && v <= 255);
-      dst[x_out] = v;
-    }
-  } else {
-    const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub);
-    const uint32_t A = (uint32_t)(WEBP_RESCALER_ONE - B);
-    for (x_out = 0; x_out < x_out_max; ++x_out) {
-      const uint64_t I = (uint64_t)A * frow[x_out]
-                       + (uint64_t)B * irow[x_out];
-      const uint32_t J = (uint32_t)((I + ROUNDER) >> WEBP_RESCALER_RFIX);
-      const int v = (int)MULT_FIX(J, wrk->fy_scale);
-      assert(v >= 0 && v <= 255);
-      dst[x_out] = v;
-    }
-  }
-}
-
-static void ExportRowShrinkC(WebPRescaler* const wrk) {
-  int x_out;
-  uint8_t* const dst = wrk->dst;
-  rescaler_t* const irow = wrk->irow;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  const rescaler_t* const frow = wrk->frow;
-  const uint32_t yscale = wrk->fy_scale * (-wrk->y_accum);
-  assert(!WebPRescalerOutputDone(wrk));
-  assert(wrk->y_accum <= 0);
-  assert(!wrk->y_expand);
-  if (yscale) {
-    for (x_out = 0; x_out < x_out_max; ++x_out) {
-      const uint32_t frac = (uint32_t)MULT_FIX(frow[x_out], yscale);
-      const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
-      assert(v >= 0 && v <= 255);
-      dst[x_out] = v;
-      irow[x_out] = frac;   // new fractional start
-    }
-  } else {
-    for (x_out = 0; x_out < x_out_max; ++x_out) {
-      const int v = (int)MULT_FIX(irow[x_out], wrk->fxy_scale);
-      assert(v >= 0 && v <= 255);
-      dst[x_out] = v;
-      irow[x_out] = 0;
-    }
-  }
-}
-
-//------------------------------------------------------------------------------
-// Main entry calls
-
-void WebPRescalerImportRow(WebPRescaler* const wrk, const uint8_t* src) {
-  assert(!WebPRescalerInputDone(wrk));
-  if (!wrk->x_expand) {
-    WebPRescalerImportRowShrink(wrk, src);
-  } else {
-    WebPRescalerImportRowExpand(wrk, src);
-  }
-}
-
-void WebPRescalerExportRow(WebPRescaler* const wrk) {
-  if (wrk->y_accum <= 0) {
-    assert(!WebPRescalerOutputDone(wrk));
-    if (wrk->y_expand) {
-      WebPRescalerExportRowExpand(wrk);
-    } else if (wrk->fxy_scale) {
-      WebPRescalerExportRowShrink(wrk);
-    } else {  // very special case for src = dst = 1x1
-      int i;
-      assert(wrk->src_width == 1 && wrk->dst_width <= 2);
-      assert(wrk->src_height == 1 && wrk->dst_height == 1);
-      for (i = 0; i < wrk->num_channels * wrk->dst_width; ++i) {
-        wrk->dst[i] = wrk->irow[i];
-        wrk->irow[i] = 0;
-      }
-    }
-    wrk->y_accum += wrk->y_add;
-    wrk->dst += wrk->dst_stride;
-    ++wrk->dst_y;
-  }
-}
-
-//------------------------------------------------------------------------------
-// MIPS version
-
-#if defined(WEBP_USE_MIPS32)
-
-static void ImportRowShrinkMIPS(WebPRescaler* const wrk, const uint8_t* src) {
-  const int x_stride = wrk->num_channels;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  const int fx_scale = wrk->fx_scale;
-  const int x_add = wrk->x_add;
-  const int x_sub = wrk->x_sub;
-  const int x_stride1 = x_stride << 2;
-  int channel;
-  assert(!wrk->x_expand);
-  assert(!WebPRescalerInputDone(wrk));
-
-  for (channel = 0; channel < x_stride; ++channel) {
-    const uint8_t* src1 = src + channel;
-    rescaler_t* frow = wrk->frow + channel;
-    int temp1, temp2, temp3;
-    int base, frac, sum;
-    int accum, accum1;
-    int loop_c = x_out_max - channel;
-
-    __asm__ volatile (
-      "li     %[temp1],   0x8000                    \n\t"
-      "li     %[temp2],   0x10000                   \n\t"
-      "li     %[sum],     0                         \n\t"
-      "li     %[accum],   0                         \n\t"
-    "1:                                             \n\t"
-      "addu   %[accum],   %[accum],   %[x_add]      \n\t"
-      "li     %[base],    0                         \n\t"
-      "blez   %[accum],   3f                        \n\t"
-    "2:                                             \n\t"
-      "lbu    %[base],    0(%[src1])                \n\t"
-      "subu   %[accum],   %[accum],   %[x_sub]      \n\t"
-      "addu   %[src1],    %[src1],    %[x_stride]   \n\t"
-      "addu   %[sum],     %[sum],     %[base]       \n\t"
-      "bgtz   %[accum],   2b                        \n\t"
-    "3:                                             \n\t"
-      "negu   %[accum1],  %[accum]                  \n\t"
-      "mul    %[frac],    %[base],    %[accum1]     \n\t"
-      "mul    %[temp3],   %[sum],     %[x_sub]      \n\t"
-      "subu   %[loop_c],  %[loop_c],  %[x_stride]   \n\t"
-      "mult   %[temp1],   %[temp2]                  \n\t"
-      "maddu  %[frac],    %[fx_scale]               \n\t"
-      "mfhi   %[sum]                                \n\t"
-      "subu   %[temp3],   %[temp3],   %[frac]       \n\t"
-      "sw     %[temp3],   0(%[frow])                \n\t"
-      "addu   %[frow],    %[frow],    %[x_stride1]  \n\t"
-      "bgtz   %[loop_c],  1b                        \n\t"
-      : [accum]"=&r"(accum), [src1]"+r"(src1), [temp3]"=&r"(temp3),
-        [sum]"=&r"(sum), [base]"=&r"(base), [frac]"=&r"(frac),
-        [frow]"+r"(frow), [accum1]"=&r"(accum1),
-        [temp2]"=&r"(temp2), [temp1]"=&r"(temp1)
-      : [x_stride]"r"(x_stride), [fx_scale]"r"(fx_scale),
-        [x_sub]"r"(x_sub), [x_add]"r"(x_add),
-        [loop_c]"r"(loop_c), [x_stride1]"r"(x_stride1)
-      : "memory", "hi", "lo"
-    );
-    assert(accum == 0);
-  }
-}
-
-static void ImportRowExpandMIPS(WebPRescaler* const wrk, const uint8_t* src) {
-  const int x_stride = wrk->num_channels;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  const int x_add = wrk->x_add;
-  const int x_sub = wrk->x_sub;
-  const int src_width = wrk->src_width;
-  const int x_stride1 = x_stride << 2;
-  int channel;
-  assert(wrk->x_expand);
-  assert(!WebPRescalerInputDone(wrk));
-
-  for (channel = 0; channel < x_stride; ++channel) {
-    const uint8_t* src1 = src + channel;
-    rescaler_t* frow = wrk->frow + channel;
-    int temp1, temp2, temp3, temp4;
-    int frac;
-    int accum;
-    int x_out = channel;
-
-    __asm__ volatile (
-      "addiu  %[temp3],   %[src_width], -1            \n\t"
-      "lbu    %[temp2],   0(%[src1])                  \n\t"
-      "addu   %[src1],    %[src1],      %[x_stride]   \n\t"
-      "bgtz   %[temp3],   0f                          \n\t"
-      "addiu  %[temp1],   %[temp2],     0             \n\t"
-      "b      3f                                      \n\t"
-    "0:                                               \n\t"
-      "lbu    %[temp1],   0(%[src1])                  \n\t"
-    "3:                                               \n\t"
-      "addiu  %[accum],   %[x_add],     0             \n\t"
-    "1:                                               \n\t"
-      "subu   %[temp3],   %[temp2],     %[temp1]      \n\t"
-      "mul    %[temp3],   %[temp3],     %[accum]      \n\t"
-      "mul    %[temp4],   %[temp1],     %[x_add]      \n\t"
-      "addu   %[temp3],   %[temp4],     %[temp3]      \n\t"
-      "sw     %[temp3],   0(%[frow])                  \n\t"
-      "addu   %[frow],    %[frow],      %[x_stride1]  \n\t"
-      "addu   %[x_out],   %[x_out],     %[x_stride]   \n\t"
-      "subu   %[temp3],   %[x_out],     %[x_out_max]  \n\t"
-      "bgez   %[temp3],   2f                          \n\t"
-      "subu   %[accum],   %[accum],     %[x_sub]      \n\t"
-      "bgez   %[accum],   4f                          \n\t"
-      "addiu  %[temp2],   %[temp1],     0             \n\t"
-      "addu   %[src1],    %[src1],      %[x_stride]   \n\t"
-      "lbu    %[temp1],   0(%[src1])                  \n\t"
-      "addu   %[accum],   %[accum],     %[x_add]      \n\t"
-    "4:                                               \n\t"
-      "b      1b                                      \n\t"
-    "2:                                               \n\t"
-      : [src1]"+r"(src1), [accum]"=&r"(accum), [temp1]"=&r"(temp1),
-        [temp2]"=&r"(temp2), [temp3]"=&r"(temp3), [temp4]"=&r"(temp4),
-        [x_out]"+r"(x_out), [frac]"=&r"(frac), [frow]"+r"(frow)
-      : [x_stride]"r"(x_stride), [x_add]"r"(x_add), [x_sub]"r"(x_sub),
-        [x_stride1]"r"(x_stride1), [src_width]"r"(src_width),
-        [x_out_max]"r"(x_out_max)
-      : "memory", "hi", "lo"
-    );
-    assert(wrk->x_sub == 0 /* <- special case for src_width=1 */ || accum == 0);
-  }
-}
-
-//------------------------------------------------------------------------------
-// Row export
-
-static void ExportRowExpandMIPS(WebPRescaler* const wrk) {
-  uint8_t* dst = wrk->dst;
-  rescaler_t* irow = wrk->irow;
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  const rescaler_t* frow = wrk->frow;
-  int temp0, temp1, temp3, temp4, temp5, loop_end;
-  const int temp2 = (int)wrk->fy_scale;
-  const int temp6 = x_out_max << 2;
-  assert(!WebPRescalerOutputDone(wrk));
-  assert(wrk->y_accum <= 0);
-  assert(wrk->y_expand);
-  assert(wrk->y_sub != 0);
-  if (wrk->y_accum == 0) {
-    __asm__ volatile (
-      "li       %[temp3],    0x10000                    \n\t"
-      "li       %[temp4],    0x8000                     \n\t"
-      "addu     %[loop_end], %[frow],     %[temp6]      \n\t"
-    "1:                                                 \n\t"
-      "lw       %[temp0],    0(%[frow])                 \n\t"
-      "addiu    %[dst],      %[dst],      1             \n\t"
-      "addiu    %[frow],     %[frow],     4             \n\t"
-      "mult     %[temp3],    %[temp4]                   \n\t"
-      "maddu    %[temp0],    %[temp2]                   \n\t"
-      "mfhi     %[temp5]                                \n\t"
-      "sb       %[temp5],    -1(%[dst])                 \n\t"
-      "bne      %[frow],     %[loop_end], 1b            \n\t"
-      : [temp0]"=&r"(temp0), [temp1]"=&r"(temp1), [temp3]"=&r"(temp3),
-        [temp4]"=&r"(temp4), [temp5]"=&r"(temp5), [frow]"+r"(frow),
-        [dst]"+r"(dst), [loop_end]"=&r"(loop_end)
-      : [temp2]"r"(temp2), [temp6]"r"(temp6)
-      : "memory", "hi", "lo"
-    );
-  } else {
-    const uint32_t B = WEBP_RESCALER_FRAC(-wrk->y_accum, wrk->y_sub);
-    const uint32_t A = (uint32_t)(WEBP_RESCALER_ONE - B);
-    __asm__ volatile (
-      "li       %[temp3],    0x10000                    \n\t"
-      "li       %[temp4],    0x8000                     \n\t"
-      "addu     %[loop_end], %[frow],     %[temp6]      \n\t"
-    "1:                                                 \n\t"
-      "lw       %[temp0],    0(%[frow])                 \n\t"
-      "lw       %[temp1],    0(%[irow])                 \n\t"
-      "addiu    %[dst],      %[dst],      1             \n\t"
-      "mult     %[temp3],    %[temp4]                   \n\t"
-      "maddu    %[A],        %[temp0]                   \n\t"
-      "maddu    %[B],        %[temp1]                   \n\t"
-      "addiu    %[frow],     %[frow],     4             \n\t"
-      "addiu    %[irow],     %[irow],     4             \n\t"
-      "mfhi     %[temp5]                                \n\t"
-      "mult     %[temp3],    %[temp4]                   \n\t"
-      "maddu    %[temp5],    %[temp2]                   \n\t"
-      "mfhi     %[temp5]                                \n\t"
-      "sb       %[temp5],    -1(%[dst])                 \n\t"
-      "bne      %[frow],     %[loop_end], 1b            \n\t"
-      : [temp0]"=&r"(temp0), [temp1]"=&r"(temp1), [temp3]"=&r"(temp3),
-        [temp4]"=&r"(temp4), [temp5]"=&r"(temp5), [frow]"+r"(frow),
-        [irow]"+r"(irow), [dst]"+r"(dst), [loop_end]"=&r"(loop_end)
-      : [temp2]"r"(temp2), [temp6]"r"(temp6), [A]"r"(A), [B]"r"(B)
-      : "memory", "hi", "lo"
-    );
-  }
-}
-
-static void ExportRowShrinkMIPS(WebPRescaler* const wrk) {
-  const int x_out_max = wrk->dst_width * wrk->num_channels;
-  uint8_t* dst = wrk->dst;
-  rescaler_t* irow = wrk->irow;
-  const rescaler_t* frow = wrk->frow;
-  const int yscale = wrk->fy_scale * (-wrk->y_accum);
-  int temp0, temp1, temp3, temp4, temp5, loop_end;
-  const int temp2 = (int)wrk->fxy_scale;
-  const int temp6 = x_out_max << 2;
-
-  assert(!WebPRescalerOutputDone(wrk));
-  assert(wrk->y_accum <= 0);
-  assert(!wrk->y_expand);
-  assert(wrk->fxy_scale != 0);
-  if (yscale) {
-    __asm__ volatile (
-      "li       %[temp3],    0x10000                    \n\t"
-      "li       %[temp4],    0x8000                     \n\t"
-      "addu     %[loop_end], %[frow],     %[temp6]      \n\t"
-    "1:                                                 \n\t"
-      "lw       %[temp0],    0(%[frow])                 \n\t"
-      "mult     %[temp3],    %[temp4]                   \n\t"
-      "addiu    %[frow],     %[frow],     4             \n\t"
-      "maddu    %[temp0],    %[yscale]                  \n\t"
-      "mfhi     %[temp1]                                \n\t"
-      "lw       %[temp0],    0(%[irow])                 \n\t"
-      "addiu    %[dst],      %[dst],      1             \n\t"
-      "addiu    %[irow],     %[irow],     4             \n\t"
-      "subu     %[temp0],    %[temp0],    %[temp1]      \n\t"
-      "mult     %[temp3],    %[temp4]                   \n\t"
-      "maddu    %[temp0],    %[temp2]                   \n\t"
-      "mfhi     %[temp5]                                \n\t"
-      "sw       %[temp1],    -4(%[irow])                \n\t"
-      "sb       %[temp5],    -1(%[dst])                 \n\t"
-      "bne      %[frow],     %[loop_end], 1b            \n\t"
-      : [temp0]"=&r"(temp0), [temp1]"=&r"(temp1), [temp3]"=&r"(temp3),
-        [temp4]"=&r"(temp4), [temp5]"=&r"(temp5), [frow]"+r"(frow),
-        [irow]"+r"(irow), [dst]"+r"(dst), [loop_end]"=&r"(loop_end)
-      : [temp2]"r"(temp2), [yscale]"r"(yscale), [temp6]"r"(temp6)
-      : "memory", "hi", "lo"
-    );
-  } else {
-    __asm__ volatile (
-      "li       %[temp3],    0x10000                    \n\t"
-      "li       %[temp4],    0x8000                     \n\t"
-      "addu     %[loop_end], %[irow],     %[temp6]      \n\t"
-    "1:                                                 \n\t"
-      "lw       %[temp0],    0(%[irow])                 \n\t"
-      "addiu    %[dst],      %[dst],      1             \n\t"
-      "addiu    %[irow],     %[irow],     4             \n\t"
-      "mult     %[temp3],    %[temp4]                   \n\t"
-      "maddu    %[temp0],    %[temp2]                   \n\t"
-      "mfhi     %[temp5]                                \n\t"
-      "sw       $zero,       -4(%[irow])                \n\t"
-      "sb       %[temp5],    -1(%[dst])                 \n\t"
-      "bne      %[irow],     %[loop_end], 1b            \n\t"
-      : [temp0]"=&r"(temp0), [temp1]"=&r"(temp1), [temp3]"=&r"(temp3),
-        [temp4]"=&r"(temp4), [temp5]"=&r"(temp5), [irow]"+r"(irow),
-        [dst]"+r"(dst), [loop_end]"=&r"(loop_end)
-      : [temp2]"r"(temp2), [temp6]"r"(temp6)
-      : "memory", "hi", "lo"
-    );
-  }
-}
-
-#endif   // WEBP_USE_MIPS32
 
 //------------------------------------------------------------------------------
 
 void WebPRescalerInit(WebPRescaler* const wrk, 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;
   wrk->x_expand = (src_width < dst_width);
@@ skipping 31 matching lines @@
     }
     wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->y_sub);
   } else {
     wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->x_add);
     // wrk->fxy_scale is unused here.
   }
   wrk->irow = work;
   wrk->frow = work + num_channels * dst_width;
   memset(work, 0, 2 * dst_width * num_channels * sizeof(*work));
 
-  if (WebPRescalerImportRowExpand == NULL) {
-    WebPRescalerImportRowExpand = ImportRowExpandC;
-    WebPRescalerImportRowShrink = ImportRowShrinkC;
-    WebPRescalerExportRowExpand = ExportRowExpandC;
-    WebPRescalerExportRowShrink = ExportRowShrinkC;
-    if (VP8GetCPUInfo != NULL) {
-#if defined(WEBP_USE_MIPS32)
-      if (VP8GetCPUInfo(kMIPS32)) {
-        WebPRescalerImportRowExpand = ImportRowExpandMIPS;
-        WebPRescalerImportRowShrink = ImportRowShrinkMIPS;
-        WebPRescalerExportRowExpand = ExportRowExpandMIPS;
-        WebPRescalerExportRowShrink = ExportRowShrinkMIPS;
-      }
-#endif
+  WebPRescalerDspInit();
+}
+
+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;
+
+    // if width is unspecified, scale original proportionally to height ratio.
+    if (width == 0) {
+      width = (src_width * height + src_height / 2) / src_height;
     }
+    // if height is unspecified, scale original proportionally to width ratio.
+    if (height == 0) {
+      height = (src_height * width + src_width / 2) / src_width;
+    }
+    // Check if the overall dimensions still make sense.
+    if (width <= 0 || height <= 0) {
+      return 0;
+    }
+
+    *scaled_width = width;
+    *scaled_height = height;
+    return 1;
   }
 }
 
-#undef MULT_FIX
-#undef WEBP_RESCALER_RFIX
-#undef WEBP_RESCALER_ONE
-#undef WEBP_RESCALER_FRAC
-#undef ROUNDER
-
 //------------------------------------------------------------------------------
 // all-in-one calls
 
 int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) {
   const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub;
   return (num_lines > max_num_lines) ? max_num_lines : num_lines;
 }
 
 int WebPRescalerImport(WebPRescaler* const wrk, int num_lines,
                        const uint8_t* src, int src_stride) {
@@ skipping 22 matching lines @@
 int WebPRescalerExport(WebPRescaler* const rescaler) {
   int total_exported = 0;
   while (WebPRescalerHasPendingOutput(rescaler)) {
     WebPRescalerExportRow(rescaler);
     ++total_exported;
   }
   return total_exported;
 }
 
 //------------------------------------------------------------------------------