146 lines
5 KiB
C
146 lines
5 KiB
C
// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Rescaling functions
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#include <assert.h>
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#include <stdlib.h>
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#include <string.h>
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#include "../dsp/dsp.h"
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#include "./rescaler.h"
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//------------------------------------------------------------------------------
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void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
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uint8_t* const dst,
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int dst_width, int dst_height, int dst_stride,
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int num_channels, rescaler_t* const work) {
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const int x_add = src_width, x_sub = dst_width;
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const int y_add = src_height, y_sub = dst_height;
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wrk->x_expand = (src_width < dst_width);
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wrk->y_expand = (src_height < dst_height);
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wrk->src_width = src_width;
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wrk->src_height = src_height;
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wrk->dst_width = dst_width;
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wrk->dst_height = dst_height;
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wrk->src_y = 0;
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wrk->dst_y = 0;
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wrk->dst = dst;
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wrk->dst_stride = dst_stride;
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wrk->num_channels = num_channels;
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// for 'x_expand', we use bilinear interpolation
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wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add;
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wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub;
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if (!wrk->x_expand) { // fx_scale is not used otherwise
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wrk->fx_scale = WEBP_RESCALER_FRAC(1, wrk->x_sub);
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}
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// vertical scaling parameters
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wrk->y_add = wrk->y_expand ? y_add - 1 : y_add;
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wrk->y_sub = wrk->y_expand ? y_sub - 1 : y_sub;
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wrk->y_accum = wrk->y_expand ? wrk->y_sub : wrk->y_add;
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if (!wrk->y_expand) {
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// This is WEBP_RESCALER_FRAC(dst_height, x_add * y_add) without the cast.
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// Its value is <= WEBP_RESCALER_ONE, because dst_height <= wrk->y_add, and
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// wrk->x_add >= 1;
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const uint64_t ratio =
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(uint64_t)dst_height * WEBP_RESCALER_ONE / (wrk->x_add * wrk->y_add);
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if (ratio != (uint32_t)ratio) {
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// When ratio == WEBP_RESCALER_ONE, we can't represent the ratio with the
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// current fixed-point precision. This happens when src_height ==
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// wrk->y_add (which == src_height), and wrk->x_add == 1.
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// => We special-case fxy_scale = 0, in WebPRescalerExportRow().
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wrk->fxy_scale = 0;
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} else {
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wrk->fxy_scale = (uint32_t)ratio;
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}
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wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->y_sub);
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} else {
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wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->x_add);
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// wrk->fxy_scale is unused here.
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}
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wrk->irow = work;
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wrk->frow = work + num_channels * dst_width;
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memset(work, 0, 2 * dst_width * num_channels * sizeof(*work));
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WebPRescalerDspInit();
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}
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int WebPRescalerGetScaledDimensions(int src_width, int src_height,
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int* const scaled_width,
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int* const scaled_height) {
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assert(scaled_width != NULL);
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assert(scaled_height != NULL);
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{
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int width = *scaled_width;
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int height = *scaled_height;
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// if width is unspecified, scale original proportionally to height ratio.
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if (width == 0) {
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width = (src_width * height + src_height / 2) / src_height;
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}
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// if height is unspecified, scale original proportionally to width ratio.
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if (height == 0) {
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height = (src_height * width + src_width / 2) / src_width;
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}
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// Check if the overall dimensions still make sense.
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if (width <= 0 || height <= 0) {
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return 0;
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}
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*scaled_width = width;
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*scaled_height = height;
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return 1;
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}
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}
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//------------------------------------------------------------------------------
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// all-in-one calls
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int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) {
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const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub;
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return (num_lines > max_num_lines) ? max_num_lines : num_lines;
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}
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int WebPRescalerImport(WebPRescaler* const wrk, int num_lines,
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const uint8_t* src, int src_stride) {
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int total_imported = 0;
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while (total_imported < num_lines && !WebPRescalerHasPendingOutput(wrk)) {
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if (wrk->y_expand) {
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rescaler_t* const tmp = wrk->irow;
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wrk->irow = wrk->frow;
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wrk->frow = tmp;
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}
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WebPRescalerImportRow(wrk, src);
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if (!wrk->y_expand) { // Accumulate the contribution of the new row.
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int x;
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for (x = 0; x < wrk->num_channels * wrk->dst_width; ++x) {
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wrk->irow[x] += wrk->frow[x];
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}
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}
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++wrk->src_y;
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src += src_stride;
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++total_imported;
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wrk->y_accum -= wrk->y_sub;
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}
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return total_imported;
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}
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int WebPRescalerExport(WebPRescaler* const rescaler) {
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int total_exported = 0;
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while (WebPRescalerHasPendingOutput(rescaler)) {
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WebPRescalerExportRow(rescaler);
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++total_exported;
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}
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return total_exported;
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}
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//------------------------------------------------------------------------------
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