1 // Copyright 2012 Google Inc. All Rights Reserved. 2 // 3 // Use of this source code is governed by a BSD-style license 4 // that can be found in the COPYING file in the root of the source 5 // tree. An additional intellectual property rights grant can be found 6 // in the file PATENTS. All contributing project authors may 7 // be found in the AUTHORS file in the root of the source tree. 8 // ----------------------------------------------------------------------------- 9 // 10 // Rescaling functions 11 // 12 // Author: Skal (pascal.massimino (at) gmail.com) 13 14 #include <assert.h> 15 #include <stdlib.h> 16 #include <string.h> 17 #include "src/dsp/dsp.h" 18 #include "src/utils/rescaler_utils.h" 19 20 //------------------------------------------------------------------------------ 21 22 void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height, 23 uint8_t* const dst, 24 int dst_width, int dst_height, int dst_stride, 25 int num_channels, rescaler_t* const work) { 26 const int x_add = src_width, x_sub = dst_width; 27 const int y_add = src_height, y_sub = dst_height; 28 wrk->x_expand = (src_width < dst_width); 29 wrk->y_expand = (src_height < dst_height); 30 wrk->src_width = src_width; 31 wrk->src_height = src_height; 32 wrk->dst_width = dst_width; 33 wrk->dst_height = dst_height; 34 wrk->src_y = 0; 35 wrk->dst_y = 0; 36 wrk->dst = dst; 37 wrk->dst_stride = dst_stride; 38 wrk->num_channels = num_channels; 39 40 // for 'x_expand', we use bilinear interpolation 41 wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add; 42 wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub; 43 if (!wrk->x_expand) { // fx_scale is not used otherwise 44 wrk->fx_scale = WEBP_RESCALER_FRAC(1, wrk->x_sub); 45 } 46 // vertical scaling parameters 47 wrk->y_add = wrk->y_expand ? y_add - 1 : y_add; 48 wrk->y_sub = wrk->y_expand ? y_sub - 1 : y_sub; 49 wrk->y_accum = wrk->y_expand ? wrk->y_sub : wrk->y_add; 50 if (!wrk->y_expand) { 51 // This is WEBP_RESCALER_FRAC(dst_height, x_add * y_add) without the cast. 52 // Its value is <= WEBP_RESCALER_ONE, because dst_height <= wrk->y_add, and 53 // wrk->x_add >= 1; 54 const uint64_t ratio = 55 (uint64_t)dst_height * WEBP_RESCALER_ONE / (wrk->x_add * wrk->y_add); 56 if (ratio != (uint32_t)ratio) { 57 // When ratio == WEBP_RESCALER_ONE, we can't represent the ratio with the 58 // current fixed-point precision. This happens when src_height == 59 // wrk->y_add (which == src_height), and wrk->x_add == 1. 60 // => We special-case fxy_scale = 0, in WebPRescalerExportRow(). 61 wrk->fxy_scale = 0; 62 } else { 63 wrk->fxy_scale = (uint32_t)ratio; 64 } 65 wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->y_sub); 66 } else { 67 wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->x_add); 68 // wrk->fxy_scale is unused here. 69 } 70 wrk->irow = work; 71 wrk->frow = work + num_channels * dst_width; 72 memset(work, 0, 2 * dst_width * num_channels * sizeof(*work)); 73 74 WebPRescalerDspInit(); 75 } 76 77 int WebPRescalerGetScaledDimensions(int src_width, int src_height, 78 int* const scaled_width, 79 int* const scaled_height) { 80 assert(scaled_width != NULL); 81 assert(scaled_height != NULL); 82 { 83 int width = *scaled_width; 84 int height = *scaled_height; 85 86 // if width is unspecified, scale original proportionally to height ratio. 87 if (width == 0) { 88 width = 89 (int)(((uint64_t)src_width * height + src_height / 2) / src_height); 90 } 91 // if height is unspecified, scale original proportionally to width ratio. 92 if (height == 0) { 93 height = 94 (int)(((uint64_t)src_height * width + src_width / 2) / src_width); 95 } 96 // Check if the overall dimensions still make sense. 97 if (width <= 0 || height <= 0) { 98 return 0; 99 } 100 101 *scaled_width = width; 102 *scaled_height = height; 103 return 1; 104 } 105 } 106 107 //------------------------------------------------------------------------------ 108 // all-in-one calls 109 110 int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) { 111 const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub; 112 return (num_lines > max_num_lines) ? max_num_lines : num_lines; 113 } 114 115 int WebPRescalerImport(WebPRescaler* const wrk, int num_lines, 116 const uint8_t* src, int src_stride) { 117 int total_imported = 0; 118 while (total_imported < num_lines && !WebPRescalerHasPendingOutput(wrk)) { 119 if (wrk->y_expand) { 120 rescaler_t* const tmp = wrk->irow; 121 wrk->irow = wrk->frow; 122 wrk->frow = tmp; 123 } 124 WebPRescalerImportRow(wrk, src); 125 if (!wrk->y_expand) { // Accumulate the contribution of the new row. 126 int x; 127 for (x = 0; x < wrk->num_channels * wrk->dst_width; ++x) { 128 wrk->irow[x] += wrk->frow[x]; 129 } 130 } 131 ++wrk->src_y; 132 src += src_stride; 133 ++total_imported; 134 wrk->y_accum -= wrk->y_sub; 135 } 136 return total_imported; 137 } 138 139 int WebPRescalerExport(WebPRescaler* const rescaler) { 140 int total_exported = 0; 141 while (WebPRescalerHasPendingOutput(rescaler)) { 142 WebPRescalerExportRow(rescaler); 143 ++total_exported; 144 } 145 return total_exported; 146 } 147 148 //------------------------------------------------------------------------------ 149
