jdpostct.c

   1 /*
   2  * jdpostct.c
   3  *
   4  * This file was part of the Independent JPEG Group's software:
   5  * Copyright (C) 1994-1996, Thomas G. Lane.
   6  * libjpeg-turbo Modifications:
   7  * Copyright (C) 2022-2023, D. R. Commander.
   8  * For conditions of distribution and use, see the accompanying README.ijg
   9  * file.
  10  *
  11  * This file contains the decompression postprocessing controller.
  12  * This controller manages the upsampling, color conversion, and color
  13  * quantization/reduction steps; specifically, it controls the buffering
  14  * between upsample/color conversion and color quantization/reduction.
  15  *
  16  * If no color quantization/reduction is required, then this module has no
  17  * work to do, and it just hands off to the upsample/color conversion code.
  18  * An integrated upsample/convert/quantize process would replace this module
  19  * entirely.
  20  */
  21
  22 #define JPEG_INTERNALS
  23 #include "jinclude.h"
  24 #include "jpeglib.h"
  25 #include "jsamplecomp.h"
  26
  27
  28 #if BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED)
  29
  30 /* Private buffer controller object */
  31
  32 typedef struct {
  33   struct jpeg_d_post_controller pub; /* public fields */
  34
  35   /* Color quantization source buffer: this holds output data from
  36    * the upsample/color conversion step to be passed to the quantizer.
  37    * For two-pass color quantization, we need a full-image buffer;
  38    * for one-pass operation, a strip buffer is sufficient.
  39    */
  40   jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
  41   _JSAMPARRAY buffer;           /* strip buffer, or current strip of virtual */
  42   JDIMENSION strip_height;      /* buffer size in rows */
  43   /* for two-pass mode only: */
  44   JDIMENSION starting_row;      /* row # of first row in current strip */
  45   JDIMENSION next_row;          /* index of next row to fill/empty in strip */
  46 } my_post_controller;
  47
  48 typedef my_post_controller *my_post_ptr;
  49
  50
  51 /* Forward declarations */
  52 #if BITS_IN_JSAMPLE != 16
  53 METHODDEF(void) post_process_1pass(j_decompress_ptr cinfo,
  54                                    _JSAMPIMAGE input_buf,
  55                                    JDIMENSION *in_row_group_ctr,
  56                                    JDIMENSION in_row_groups_avail,
  57                                    _JSAMPARRAY output_buf,
  58                                    JDIMENSION *out_row_ctr,
  59                                    JDIMENSION out_rows_avail);
  60 #endif
  61 #if defined(QUANT_2PASS_SUPPORTED) && BITS_IN_JSAMPLE != 16
  62 METHODDEF(void) post_process_prepass(j_decompress_ptr cinfo,
  63                                      _JSAMPIMAGE input_buf,
  64                                      JDIMENSION *in_row_group_ctr,
  65                                      JDIMENSION in_row_groups_avail,
  66                                      _JSAMPARRAY output_buf,
  67                                      JDIMENSION *out_row_ctr,
  68                                      JDIMENSION out_rows_avail);
  69 METHODDEF(void) post_process_2pass(j_decompress_ptr cinfo,
  70                                    _JSAMPIMAGE input_buf,
  71                                    JDIMENSION *in_row_group_ctr,
  72                                    JDIMENSION in_row_groups_avail,
  73                                    _JSAMPARRAY output_buf,
  74                                    JDIMENSION *out_row_ctr,
  75                                    JDIMENSION out_rows_avail);
  76 #endif
  77
  78
  79 /*
  80  * Initialize for a processing pass.
  81  */
  82
  83 METHODDEF(void)
  84 start_pass_dpost(j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
  85 {
  86   my_post_ptr post = (my_post_ptr)cinfo->post;
  87
  88   switch (pass_mode) {
  89   case JBUF_PASS_THRU:
  90 #if BITS_IN_JSAMPLE != 16
  91     if (cinfo->quantize_colors) {
  92       /* Single-pass processing with color quantization. */
  93       post->pub._post_process_data = post_process_1pass;
  94       /* We could be doing buffered-image output before starting a 2-pass
  95        * color quantization; in that case, jinit_d_post_controller did not
  96        * allocate a strip buffer.  Use the virtual-array buffer as workspace.
  97        */
  98       if (post->buffer == NULL) {
  99         post->buffer = (_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
 100           ((j_common_ptr)cinfo, post->whole_image,
 101            (JDIMENSION)0, post->strip_height, TRUE);
 102       }
 103     } else
 104 #endif
 105     {
 106       /* For single-pass processing without color quantization,
 107        * I have no work to do; just call the upsampler directly.
 108        */
 109       post->pub._post_process_data = cinfo->upsample->_upsample;
 110     }
 111     break;
 112 #if defined(QUANT_2PASS_SUPPORTED) && BITS_IN_JSAMPLE != 16
 113   case JBUF_SAVE_AND_PASS:
 114     /* First pass of 2-pass quantization */
 115     if (post->whole_image == NULL)
 116       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 117     post->pub._post_process_data = post_process_prepass;
 118     break;
 119   case JBUF_CRANK_DEST:
 120     /* Second pass of 2-pass quantization */
 121     if (post->whole_image == NULL)
 122       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 123     post->pub._post_process_data = post_process_2pass;
 124     break;
 125 #endif /* defined(QUANT_2PASS_SUPPORTED) && BITS_IN_JSAMPLE != 16 */
 126   default:
 127     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 128     break;
 129   }
 130   post->starting_row = post->next_row = 0;
 131 }
 132
 133
 134 /*
 135  * Process some data in the one-pass (strip buffer) case.
 136  * This is used for color precision reduction as well as one-pass quantization.
 137  */
 138
 139 #if BITS_IN_JSAMPLE != 16
 140
 141 METHODDEF(void)
 142 post_process_1pass(j_decompress_ptr cinfo, _JSAMPIMAGE input_buf,
 143                    JDIMENSION *in_row_group_ctr,
 144                    JDIMENSION in_row_groups_avail, _JSAMPARRAY output_buf,
 145                    JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
 146 {
 147   my_post_ptr post = (my_post_ptr)cinfo->post;
 148   JDIMENSION num_rows, max_rows;
 149
 150   /* Fill the buffer, but not more than what we can dump out in one go. */
 151   /* Note we rely on the upsampler to detect bottom of image. */
 152   max_rows = out_rows_avail - *out_row_ctr;
 153   if (max_rows > post->strip_height)
 154     max_rows = post->strip_height;
 155   num_rows = 0;
 156   (*cinfo->upsample->_upsample) (cinfo, input_buf, in_row_group_ctr,
 157                                  in_row_groups_avail, post->buffer, &num_rows,
 158                                  max_rows);
 159   /* Quantize and emit data. */
 160   (*cinfo->cquantize->_color_quantize) (cinfo, post->buffer,
 161                                         output_buf + *out_row_ctr,
 162                                         (int)num_rows);
 163   *out_row_ctr += num_rows;
 164 }
 165
 166 #endif
 167
 168
 169 #if defined(QUANT_2PASS_SUPPORTED) && BITS_IN_JSAMPLE != 16
 170
 171 /*
 172  * Process some data in the first pass of 2-pass quantization.
 173  */
 174
 175 METHODDEF(void)
 176 post_process_prepass(j_decompress_ptr cinfo, _JSAMPIMAGE input_buf,
 177                      JDIMENSION *in_row_group_ctr,
 178                      JDIMENSION in_row_groups_avail, _JSAMPARRAY output_buf,
 179                      JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
 180 {
 181   my_post_ptr post = (my_post_ptr)cinfo->post;
 182   JDIMENSION old_next_row, num_rows;
 183
 184   /* Reposition virtual buffer if at start of strip. */
 185   if (post->next_row == 0) {
 186     post->buffer = (_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
 187         ((j_common_ptr)cinfo, post->whole_image,
 188          post->starting_row, post->strip_height, TRUE);
 189   }
 190
 191   /* Upsample some data (up to a strip height's worth). */
 192   old_next_row = post->next_row;
 193   (*cinfo->upsample->_upsample) (cinfo, input_buf, in_row_group_ctr,
 194                                  in_row_groups_avail, post->buffer,
 195                                  &post->next_row, post->strip_height);
 196
 197   /* Allow quantizer to scan new data.  No data is emitted, */
 198   /* but we advance out_row_ctr so outer loop can tell when we're done. */
 199   if (post->next_row > old_next_row) {
 200     num_rows = post->next_row - old_next_row;
 201     (*cinfo->cquantize->_color_quantize) (cinfo, post->buffer + old_next_row,
 202                                           (_JSAMPARRAY)NULL, (int)num_rows);
 203     *out_row_ctr += num_rows;
 204   }
 205
 206   /* Advance if we filled the strip. */
 207   if (post->next_row >= post->strip_height) {
 208     post->starting_row += post->strip_height;
 209     post->next_row = 0;
 210   }
 211 }
 212
 213
 214 /*
 215  * Process some data in the second pass of 2-pass quantization.
 216  */
 217
 218 METHODDEF(void)
 219 post_process_2pass(j_decompress_ptr cinfo, _JSAMPIMAGE input_buf,
 220                    JDIMENSION *in_row_group_ctr,
 221                    JDIMENSION in_row_groups_avail, _JSAMPARRAY output_buf,
 222                    JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
 223 {
 224   my_post_ptr post = (my_post_ptr)cinfo->post;
 225   JDIMENSION num_rows, max_rows;
 226
 227   /* Reposition virtual buffer if at start of strip. */
 228   if (post->next_row == 0) {
 229     post->buffer = (_JSAMPARRAY)(*cinfo->mem->access_virt_sarray)
 230         ((j_common_ptr)cinfo, post->whole_image,
 231          post->starting_row, post->strip_height, FALSE);
 232   }
 233
 234   /* Determine number of rows to emit. */
 235   num_rows = post->strip_height - post->next_row; /* available in strip */
 236   max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
 237   if (num_rows > max_rows)
 238     num_rows = max_rows;
 239   /* We have to check bottom of image here, can't depend on upsampler. */
 240   max_rows = cinfo->output_height - post->starting_row;
 241   if (num_rows > max_rows)
 242     num_rows = max_rows;
 243
 244   /* Quantize and emit data. */
 245   (*cinfo->cquantize->_color_quantize) (cinfo, post->buffer + post->next_row,
 246                                         output_buf + *out_row_ctr,
 247                                         (int)num_rows);
 248   *out_row_ctr += num_rows;
 249
 250   /* Advance if we filled the strip. */
 251   post->next_row += num_rows;
 252   if (post->next_row >= post->strip_height) {
 253     post->starting_row += post->strip_height;
 254     post->next_row = 0;
 255   }
 256 }
 257
 258 #endif /* defined(QUANT_2PASS_SUPPORTED) && BITS_IN_JSAMPLE != 16 */
 259
 260
 261 /*
 262  * Initialize postprocessing controller.
 263  */
 264
 265 GLOBAL(void)
 266 _jinit_d_post_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
 267 {
 268   my_post_ptr post;
 269
 270   if (cinfo->data_precision != BITS_IN_JSAMPLE)
 271     ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
 272
 273   post = (my_post_ptr)
 274     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 275                                 sizeof(my_post_controller));
 276   cinfo->post = (struct jpeg_d_post_controller *)post;
 277   post->pub.start_pass = start_pass_dpost;
 278   post->whole_image = NULL;     /* flag for no virtual arrays */
 279   post->buffer = NULL;          /* flag for no strip buffer */
 280
 281   /* Create the quantization buffer, if needed */
 282   if (cinfo->quantize_colors) {
 283 #if BITS_IN_JSAMPLE != 16
 284     /* The buffer strip height is max_v_samp_factor, which is typically
 285      * an efficient number of rows for upsampling to return.
 286      * (In the presence of output rescaling, we might want to be smarter?)
 287      */
 288     post->strip_height = (JDIMENSION)cinfo->max_v_samp_factor;
 289     if (need_full_buffer) {
 290       /* Two-pass color quantization: need full-image storage. */
 291       /* We round up the number of rows to a multiple of the strip height. */
 292 #ifdef QUANT_2PASS_SUPPORTED
 293       post->whole_image = (*cinfo->mem->request_virt_sarray)
 294         ((j_common_ptr)cinfo, JPOOL_IMAGE, FALSE,
 295          cinfo->output_width * cinfo->out_color_components,
 296          (JDIMENSION)jround_up((long)cinfo->output_height,
 297                                (long)post->strip_height),
 298          post->strip_height);
 299 #else
 300       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 301 #endif /* QUANT_2PASS_SUPPORTED */
 302     } else {
 303       /* One-pass color quantization: just make a strip buffer. */
 304       post->buffer = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
 305         ((j_common_ptr)cinfo, JPOOL_IMAGE,
 306          cinfo->output_width * cinfo->out_color_components,
 307          post->strip_height);
 308     }
 309 #else
 310     ERREXIT(cinfo, JERR_NOTIMPL);
 311 #endif
 312   }
 313 }
 314
 315 #endif /* BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED) */