libwebp: update to 0.5.0

This commit imports libwebp 0.5.0, including AUTHORS, COPYING, ChangeLog,
NEWS, PATENTS, README and src directories. In src, only includes header
and source files.

The patches required to build it in Qt will follow in separate
commit(s).

Change-Id: I96b4961ba63c75cc7fbab158c36a0f403f254c14
Reviewed-by: aavit <eirik.aavitsland@theqtcompany.com>

1 files changed, 28 insertions, 464 deletions

diff --git a/src/3rdparty/libwebp/src/utils/rescaler.c b/src/3rdparty/libwebp/src/utils/rescaler.c
index 3a43229..00c9300 100644
--- a/src/3rdparty/libwebp/src/utils/rescaler.c
+++ b/src/3rdparty/libwebp/src/utils/rescaler.c
@@ -14,451 +14,8 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <string.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
+#include "./rescaler.h"
 
 //------------------------------------------------------------------------------
 
@@ -510,30 +67,37 @@ void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
   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