1/* 2 * jdsample.c 3 * 4 * Copyright (C) 1991-1996, Thomas G. Lane. 5 * Modified 2002-2008 by Guido Vollbeding. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains upsampling routines. 10 * 11 * Upsampling input data is counted in "row groups". A row group 12 * is defined to be (v_samp_factor * DCT_v_scaled_size / min_DCT_v_scaled_size) 13 * sample rows of each component. Upsampling will normally produce 14 * max_v_samp_factor pixel rows from each row group (but this could vary 15 * if the upsampler is applying a scale factor of its own). 16 * 17 * An excellent reference for image resampling is 18 * Digital Image Warping, George Wolberg, 1990. 19 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7. 20 */ 21 22#define JPEG_INTERNALS 23#include "jinclude.h" 24#include "jpeglib.h" 25 26 27/* Pointer to routine to upsample a single component */ 28typedef JMETHOD(void, upsample1_ptr, 29 (j_decompress_ptr cinfo, jpeg_component_info * compptr, 30 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)); 31 32/* Private subobject */ 33 34typedef struct { 35 struct jpeg_upsampler pub; /* public fields */ 36 37 /* Color conversion buffer. When using separate upsampling and color 38 * conversion steps, this buffer holds one upsampled row group until it 39 * has been color converted and output. 40 * Note: we do not allocate any storage for component(s) which are full-size, 41 * ie do not need rescaling. The corresponding entry of color_buf[] is 42 * simply set to point to the input data array, thereby avoiding copying. 43 */ 44 JSAMPARRAY color_buf[MAX_COMPONENTS]; 45 46 /* Per-component upsampling method pointers */ 47 upsample1_ptr methods[MAX_COMPONENTS]; 48 49 int next_row_out; /* counts rows emitted from color_buf */ 50 JDIMENSION rows_to_go; /* counts rows remaining in image */ 51 52 /* Height of an input row group for each component. */ 53 int rowgroup_height[MAX_COMPONENTS]; 54 55 /* These arrays save pixel expansion factors so that int_expand need not 56 * recompute them each time. They are unused for other upsampling methods. 57 */ 58 UINT8 h_expand[MAX_COMPONENTS]; 59 UINT8 v_expand[MAX_COMPONENTS]; 60} my_upsampler; 61 62typedef my_upsampler * my_upsample_ptr; 63 64 65/* 66 * Initialize for an upsampling pass. 67 */ 68 69METHODDEF(void) 70start_pass_upsample (j_decompress_ptr cinfo) 71{ 72 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 73 74 /* Mark the conversion buffer empty */ 75 upsample->next_row_out = cinfo->max_v_samp_factor; 76 /* Initialize total-height counter for detecting bottom of image */ 77 upsample->rows_to_go = cinfo->output_height; 78} 79 80 81/* 82 * Control routine to do upsampling (and color conversion). 83 * 84 * In this version we upsample each component independently. 85 * We upsample one row group into the conversion buffer, then apply 86 * color conversion a row at a time. 87 */ 88 89METHODDEF(void) 90sep_upsample (j_decompress_ptr cinfo, 91 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 92 JDIMENSION in_row_groups_avail, 93 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 94 JDIMENSION out_rows_avail) 95{ 96 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 97 int ci; 98 jpeg_component_info * compptr; 99 JDIMENSION num_rows; 100 101 /* Fill the conversion buffer, if it's empty */ 102 if (upsample->next_row_out >= cinfo->max_v_samp_factor) { 103 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 104 ci++, compptr++) { 105 /* Invoke per-component upsample method. Notice we pass a POINTER 106 * to color_buf[ci], so that fullsize_upsample can change it. 107 */ 108 (*upsample->methods[ci]) (cinfo, compptr, 109 input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]), 110 upsample->color_buf + ci); 111 } 112 upsample->next_row_out = 0; 113 } 114 115 /* Color-convert and emit rows */ 116 117 /* How many we have in the buffer: */ 118 num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out); 119 /* Not more than the distance to the end of the image. Need this test 120 * in case the image height is not a multiple of max_v_samp_factor: 121 */ 122 if (num_rows > upsample->rows_to_go) 123 num_rows = upsample->rows_to_go; 124 /* And not more than what the client can accept: */ 125 out_rows_avail -= *out_row_ctr; 126 if (num_rows > out_rows_avail) 127 num_rows = out_rows_avail; 128 129 (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf, 130 (JDIMENSION) upsample->next_row_out, 131 output_buf + *out_row_ctr, 132 (int) num_rows); 133 134 /* Adjust counts */ 135 *out_row_ctr += num_rows; 136 upsample->rows_to_go -= num_rows; 137 upsample->next_row_out += num_rows; 138 /* When the buffer is emptied, declare this input row group consumed */ 139 if (upsample->next_row_out >= cinfo->max_v_samp_factor) 140 (*in_row_group_ctr)++; 141} 142 143 144/* 145 * These are the routines invoked by sep_upsample to upsample pixel values 146 * of a single component. One row group is processed per call. 147 */ 148 149 150/* 151 * For full-size components, we just make color_buf[ci] point at the 152 * input buffer, and thus avoid copying any data. Note that this is 153 * safe only because sep_upsample doesn't declare the input row group 154 * "consumed" until we are done color converting and emitting it. 155 */ 156 157METHODDEF(void) 158fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 159 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 160{ 161 *output_data_ptr = input_data; 162} 163 164 165/* 166 * This is a no-op version used for "uninteresting" components. 167 * These components will not be referenced by color conversion. 168 */ 169 170METHODDEF(void) 171noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 172 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 173{ 174 *output_data_ptr = NULL; /* safety check */ 175} 176 177 178/* 179 * This version handles any integral sampling ratios. 180 * This is not used for typical JPEG files, so it need not be fast. 181 * Nor, for that matter, is it particularly accurate: the algorithm is 182 * simple replication of the input pixel onto the corresponding output 183 * pixels. The hi-falutin sampling literature refers to this as a 184 * "box filter". A box filter tends to introduce visible artifacts, 185 * so if you are actually going to use 3:1 or 4:1 sampling ratios 186 * you would be well advised to improve this code. 187 */ 188 189METHODDEF(void) 190int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 191 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 192{ 193 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 194 JSAMPARRAY output_data = *output_data_ptr; 195 register JSAMPROW inptr, outptr; 196 register JSAMPLE invalue; 197 register int h; 198 JSAMPROW outend; 199 int h_expand, v_expand; 200 int inrow, outrow; 201 202 h_expand = upsample->h_expand[compptr->component_index]; 203 v_expand = upsample->v_expand[compptr->component_index]; 204 205 inrow = outrow = 0; 206 while (outrow < cinfo->max_v_samp_factor) { 207 /* Generate one output row with proper horizontal expansion */ 208 inptr = input_data[inrow]; 209 outptr = output_data[outrow]; 210 outend = outptr + cinfo->output_width; 211 while (outptr < outend) { 212 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 213 for (h = h_expand; h > 0; h--) { 214 *outptr++ = invalue; 215 } 216 } 217 /* Generate any additional output rows by duplicating the first one */ 218 if (v_expand > 1) { 219 jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 220 v_expand-1, cinfo->output_width); 221 } 222 inrow++; 223 outrow += v_expand; 224 } 225} 226 227 228/* 229 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical. 230 * It's still a box filter. 231 */ 232 233METHODDEF(void) 234h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 235 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 236{ 237 JSAMPARRAY output_data = *output_data_ptr; 238 register JSAMPROW inptr, outptr; 239 register JSAMPLE invalue; 240 JSAMPROW outend; 241 int outrow; 242 243 for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) { 244 inptr = input_data[outrow]; 245 outptr = output_data[outrow]; 246 outend = outptr + cinfo->output_width; 247 while (outptr < outend) { 248 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 249 *outptr++ = invalue; 250 *outptr++ = invalue; 251 } 252 } 253} 254 255 256/* 257 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical. 258 * It's still a box filter. 259 */ 260 261METHODDEF(void) 262h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 263 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 264{ 265 JSAMPARRAY output_data = *output_data_ptr; 266 register JSAMPROW inptr, outptr; 267 register JSAMPLE invalue; 268 JSAMPROW outend; 269 int inrow, outrow; 270 271 inrow = outrow = 0; 272 while (outrow < cinfo->max_v_samp_factor) { 273 inptr = input_data[inrow]; 274 outptr = output_data[outrow]; 275 outend = outptr + cinfo->output_width; 276 while (outptr < outend) { 277 invalue = *inptr++; /* don't need GETJSAMPLE() here */ 278 *outptr++ = invalue; 279 *outptr++ = invalue; 280 } 281 jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 282 1, cinfo->output_width); 283 inrow++; 284 outrow += 2; 285 } 286} 287 288 289/* 290 * Module initialization routine for upsampling. 291 */ 292 293GLOBAL(void) 294jinit_upsampler (j_decompress_ptr cinfo) 295{ 296 my_upsample_ptr upsample; 297 int ci; 298 jpeg_component_info * compptr; 299 boolean need_buffer; 300 int h_in_group, v_in_group, h_out_group, v_out_group; 301 302 upsample = (my_upsample_ptr) 303 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 304 SIZEOF(my_upsampler)); 305 cinfo->upsample = (struct jpeg_upsampler *) upsample; 306 upsample->pub.start_pass = start_pass_upsample; 307 upsample->pub.upsample = sep_upsample; 308 upsample->pub.need_context_rows = FALSE; /* until we find out differently */ 309 310 if (cinfo->CCIR601_sampling) /* this isn't supported */ 311 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL); 312 313 /* Verify we can handle the sampling factors, select per-component methods, 314 * and create storage as needed. 315 */ 316 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 317 ci++, compptr++) { 318 /* Compute size of an "input group" after IDCT scaling. This many samples 319 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels. 320 */ 321 h_in_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) / 322 cinfo->min_DCT_h_scaled_size; 323 v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) / 324 cinfo->min_DCT_v_scaled_size; 325 h_out_group = cinfo->max_h_samp_factor; 326 v_out_group = cinfo->max_v_samp_factor; 327 upsample->rowgroup_height[ci] = v_in_group; /* save for use later */ 328 need_buffer = TRUE; 329 if (! compptr->component_needed) { 330 /* Don't bother to upsample an uninteresting component. */ 331 upsample->methods[ci] = noop_upsample; 332 need_buffer = FALSE; 333 } else if (h_in_group == h_out_group && v_in_group == v_out_group) { 334 /* Fullsize components can be processed without any work. */ 335 upsample->methods[ci] = fullsize_upsample; 336 need_buffer = FALSE; 337 } else if (h_in_group * 2 == h_out_group && 338 v_in_group == v_out_group) { 339 /* Special case for 2h1v upsampling */ 340 upsample->methods[ci] = h2v1_upsample; 341 } else if (h_in_group * 2 == h_out_group && 342 v_in_group * 2 == v_out_group) { 343 /* Special case for 2h2v upsampling */ 344 upsample->methods[ci] = h2v2_upsample; 345 } else if ((h_out_group % h_in_group) == 0 && 346 (v_out_group % v_in_group) == 0) { 347 /* Generic integral-factors upsampling method */ 348 upsample->methods[ci] = int_upsample; 349 upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group); 350 upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group); 351 } else 352 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL); 353 if (need_buffer) { 354 upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray) 355 ((j_common_ptr) cinfo, JPOOL_IMAGE, 356 (JDIMENSION) jround_up((long) cinfo->output_width, 357 (long) cinfo->max_h_samp_factor), 358 (JDIMENSION) cinfo->max_v_samp_factor); 359 } 360 } 361} 362