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