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 "../dsp/dsp.h" 18 #include "./rescaler.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 const uint64_t ratio = 53 (uint64_t)dst_height * WEBP_RESCALER_ONE / (wrk->x_add * wrk->y_add); 54 if (ratio != (uint32_t)ratio) { 55 // We can't represent the ratio with the current fixed-point precision. 56 // => We special-case fxy_scale = 0, in WebPRescalerExportRow(). 57 wrk->fxy_scale = 0; 58 } else { 59 wrk->fxy_scale = (uint32_t)ratio; 60 } 61 wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->y_sub); 62 } else { 63 wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->x_add); 64 // wrk->fxy_scale is unused here. 65 } 66 wrk->irow = work; 67 wrk->frow = work + num_channels * dst_width; 68 memset(work, 0, 2 * dst_width * num_channels * sizeof(*work)); 69 70 WebPRescalerDspInit(); 71 } 72 73 int WebPRescalerGetScaledDimensions(int src_width, int src_height, 74 int* const scaled_width, 75 int* const scaled_height) { 76 assert(scaled_width != NULL); 77 assert(scaled_height != NULL); 78 { 79 int width = *scaled_width; 80 int height = *scaled_height; 81 82 // if width is unspecified, scale original proportionally to height ratio. 83 if (width == 0) { 84 width = (src_width * height + src_height / 2) / src_height; 85 } 86 // if height is unspecified, scale original proportionally to width ratio. 87 if (height == 0) { 88 height = (src_height * width + src_width / 2) / src_width; 89 } 90 // Check if the overall dimensions still make sense. 91 if (width <= 0 || height <= 0) { 92 return 0; 93 } 94 95 *scaled_width = width; 96 *scaled_height = height; 97 return 1; 98 } 99 } 100 101 //------------------------------------------------------------------------------ 102 // all-in-one calls 103 104 int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) { 105 const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub; 106 return (num_lines > max_num_lines) ? max_num_lines : num_lines; 107 } 108 109 int WebPRescalerImport(WebPRescaler* const wrk, int num_lines, 110 const uint8_t* src, int src_stride) { 111 int total_imported = 0; 112 while (total_imported < num_lines && !WebPRescalerHasPendingOutput(wrk)) { 113 if (wrk->y_expand) { 114 rescaler_t* const tmp = wrk->irow; 115 wrk->irow = wrk->frow; 116 wrk->frow = tmp; 117 } 118 WebPRescalerImportRow(wrk, src); 119 if (!wrk->y_expand) { // Accumulate the contribution of the new row. 120 int x; 121 for (x = 0; x < wrk->num_channels * wrk->dst_width; ++x) { 122 wrk->irow[x] += wrk->frow[x]; 123 } 124 } 125 ++wrk->src_y; 126 src += src_stride; 127 ++total_imported; 128 wrk->y_accum -= wrk->y_sub; 129 } 130 return total_imported; 131 } 132 133 int WebPRescalerExport(WebPRescaler* const rescaler) { 134 int total_exported = 0; 135 while (WebPRescalerHasPendingOutput(rescaler)) { 136 WebPRescalerExportRow(rescaler); 137 ++total_exported; 138 } 139 return total_exported; 140 } 141 142 //------------------------------------------------------------------------------ 143