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