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   1 /*
   2  * jdpostct.c
   3  *
   4  * Copyright (C) 1994-1996, Thomas G. Lane.
   5  * This file is part of the Independent JPEG Group's software.
   6  * For conditions of distribution and use, see the accompanying README file.
   7  *
   8  * This file contains the decompression postprocessing controller.
   9  * This controller manages the upsampling, color conversion, and color
  10  * quantization/reduction steps; specifically, it controls the buffering
  11  * between upsample/color conversion and color quantization/reduction.
  12  *
  13  * If no color quantization/reduction is required, then this module has no
  14  * work to do, and it just hands off to the upsample/color conversion code.
  15  * An integrated upsample/convert/quantize process would replace this module
  16  * entirely.
  17  */
  18
  19 #define JPEG_INTERNALS
  20 #include "jinclude.h"
  21 #include "jpeglib.h"
  22
  23
  24 /* Private buffer controller object */
  25
  26 typedef struct {
  27   struct jpeg_d_post_controller pub; /* public fields */
  28
  29   /* Color quantization source buffer: this holds output data from
  30    * the upsample/color conversion step to be passed to the quantizer.
  31    * For two-pass color quantization, we need a full-image buffer;
  32    * for one-pass operation, a strip buffer is sufficient.
  33    */
  34   jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
  35   JSAMPARRAY buffer;            /* strip buffer, or current strip of virtual */
  36   JDIMENSION strip_height;      /* buffer size in rows */
  37   /* for two-pass mode only: */
  38   JDIMENSION starting_row;      /* row # of first row in current strip */
  39   JDIMENSION next_row;          /* index of next row to fill/empty in strip */
  40 } my_post_controller;
  41
  42 typedef my_post_controller * my_post_ptr;
  43
  44
  45 /* Forward declarations */
  46 METHODDEF(void) post_process_1pass
  47         JPP((j_decompress_ptr cinfo,
  48              JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
  49              JDIMENSION in_row_groups_avail,
  50              JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
  51              JDIMENSION out_rows_avail));
  52 #ifdef QUANT_2PASS_SUPPORTED
  53 METHODDEF(void) post_process_prepass
  54         JPP((j_decompress_ptr cinfo,
  55              JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
  56              JDIMENSION in_row_groups_avail,
  57              JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
  58              JDIMENSION out_rows_avail));
  59 METHODDEF(void) post_process_2pass
  60         JPP((j_decompress_ptr cinfo,
  61              JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
  62              JDIMENSION in_row_groups_avail,
  63              JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
  64              JDIMENSION out_rows_avail));
  65 #endif
  66
  67
  68 /*
  69  * Initialize for a processing pass.
  70  */
  71
  72 METHODDEF(void)
  73 start_pass_dpost (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
  74 {
  75   my_post_ptr post = (my_post_ptr) cinfo->post;
  76
  77   switch (pass_mode) {
  78   case JBUF_PASS_THRU:
  79     if (cinfo->quantize_colors) {
  80       /* Single-pass processing with color quantization. */
  81       post->pub.post_process_data = post_process_1pass;
  82       /* We could be doing buffered-image output before starting a 2-pass
  83        * color quantization; in that case, jinit_d_post_controller did not
  84        * allocate a strip buffer.  Use the virtual-array buffer as workspace.
  85        */
  86       if (post->buffer == NULL) {
  87         post->buffer = (*cinfo->mem->access_virt_sarray)
  88           ((j_common_ptr) cinfo, post->whole_image,
  89            (JDIMENSION) 0, post->strip_height, TRUE);
  90       }
  91     } else {
  92       /* For single-pass processing without color quantization,
  93        * I have no work to do; just call the upsampler directly.
  94        */
  95       post->pub.post_process_data = cinfo->upsample->upsample;
  96     }
  97     break;
  98 #ifdef QUANT_2PASS_SUPPORTED
  99   case JBUF_SAVE_AND_PASS:
 100     /* First pass of 2-pass quantization */
 101     if (post->whole_image == NULL)
 102       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 103     post->pub.post_process_data = post_process_prepass;
 104     break;
 105   case JBUF_CRANK_DEST:
 106     /* Second 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_2pass;
 110     break;
 111 #endif /* QUANT_2PASS_SUPPORTED */
 112   default:
 113     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 114     break;
 115   }
 116   post->starting_row = post->next_row = 0;
 117 }
 118
 119
 120 /*
 121  * Process some data in the one-pass (strip buffer) case.
 122  * This is used for color precision reduction as well as one-pass quantization.
 123  */
 124
 125 METHODDEF(void)
 126 post_process_1pass (j_decompress_ptr cinfo,
 127                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 128                     JDIMENSION in_row_groups_avail,
 129                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 130                     JDIMENSION out_rows_avail)
 131 {
 132   my_post_ptr post = (my_post_ptr) cinfo->post;
 133   JDIMENSION num_rows, max_rows;
 134
 135   /* Fill the buffer, but not more than what we can dump out in one go. */
 136   /* Note we rely on the upsampler to detect bottom of image. */
 137   max_rows = out_rows_avail - *out_row_ctr;
 138   if (max_rows > post->strip_height)
 139     max_rows = post->strip_height;
 140   num_rows = 0;
 141   (*cinfo->upsample->upsample) (cinfo,
 142                 input_buf, in_row_group_ctr, in_row_groups_avail,
 143                 post->buffer, &num_rows, max_rows);
 144   /* Quantize and emit data. */
 145   (*cinfo->cquantize->color_quantize) (cinfo,
 146                 post->buffer, output_buf + *out_row_ctr, (int) num_rows);
 147   *out_row_ctr += num_rows;
 148 }
 149
 150
 151 #ifdef QUANT_2PASS_SUPPORTED
 152
 153 /*
 154  * Process some data in the first pass of 2-pass quantization.
 155  */
 156
 157 METHODDEF(void)
 158 post_process_prepass (j_decompress_ptr cinfo,
 159                       JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 160                       JDIMENSION in_row_groups_avail,
 161                       JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 162                       JDIMENSION out_rows_avail)
 163 {
 164   my_post_ptr post = (my_post_ptr) cinfo->post;
 165   JDIMENSION old_next_row, num_rows;
 166
 167   /* Reposition virtual buffer if at start of strip. */
 168   if (post->next_row == 0) {
 169     post->buffer = (*cinfo->mem->access_virt_sarray)
 170         ((j_common_ptr) cinfo, post->whole_image,
 171          post->starting_row, post->strip_height, TRUE);
 172   }
 173
 174   /* Upsample some data (up to a strip height's worth). */
 175   old_next_row = post->next_row;
 176   (*cinfo->upsample->upsample) (cinfo,
 177                 input_buf, in_row_group_ctr, in_row_groups_avail,
 178                 post->buffer, &post->next_row, post->strip_height);
 179
 180   /* Allow quantizer to scan new data.  No data is emitted, */
 181   /* but we advance out_row_ctr so outer loop can tell when we're done. */
 182   if (post->next_row > old_next_row) {
 183     num_rows = post->next_row - old_next_row;
 184     (*cinfo->cquantize->color_quantize) (cinfo, post->buffer + old_next_row,
 185                                          (JSAMPARRAY) NULL, (int) num_rows);
 186     *out_row_ctr += num_rows;
 187   }
 188
 189   /* Advance if we filled the strip. */
 190   if (post->next_row >= post->strip_height) {
 191     post->starting_row += post->strip_height;
 192     post->next_row = 0;
 193   }
 194 }
 195
 196
 197 /*
 198  * Process some data in the second pass of 2-pass quantization.
 199  */
 200
 201 METHODDEF(void)
 202 post_process_2pass (j_decompress_ptr cinfo,
 203                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 204                     JDIMENSION in_row_groups_avail,
 205                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 206                     JDIMENSION out_rows_avail)
 207 {
 208   my_post_ptr post = (my_post_ptr) cinfo->post;
 209   JDIMENSION num_rows, max_rows;
 210
 211   /* Reposition virtual buffer if at start of strip. */
 212   if (post->next_row == 0) {
 213     post->buffer = (*cinfo->mem->access_virt_sarray)
 214         ((j_common_ptr) cinfo, post->whole_image,
 215          post->starting_row, post->strip_height, FALSE);
 216   }
 217
 218   /* Determine number of rows to emit. */
 219   num_rows = post->strip_height - post->next_row; /* available in strip */
 220   max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
 221   if (num_rows > max_rows)
 222     num_rows = max_rows;
 223   /* We have to check bottom of image here, can't depend on upsampler. */
 224   max_rows = cinfo->output_height - post->starting_row;
 225   if (num_rows > max_rows)
 226     num_rows = max_rows;
 227
 228   /* Quantize and emit data. */
 229   (*cinfo->cquantize->color_quantize) (cinfo,
 230                 post->buffer + post->next_row, output_buf + *out_row_ctr,
 231                 (int) num_rows);
 232   *out_row_ctr += num_rows;
 233
 234   /* Advance if we filled the strip. */
 235   post->next_row += num_rows;
 236   if (post->next_row >= post->strip_height) {
 237     post->starting_row += post->strip_height;
 238     post->next_row = 0;
 239   }
 240 }
 241
 242 #endif /* QUANT_2PASS_SUPPORTED */
 243
 244
 245 /*
 246  * Initialize postprocessing controller.
 247  */
 248
 249 GLOBAL(void)
 250 jinit_d_post_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
 251 {
 252   my_post_ptr post;
 253
 254   post = (my_post_ptr)
 255     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 256                                 SIZEOF(my_post_controller));
 257   cinfo->post = (struct jpeg_d_post_controller *) post;
 258   post->pub.start_pass = start_pass_dpost;
 259   post->whole_image = NULL;     /* flag for no virtual arrays */
 260   post->buffer = NULL;          /* flag for no strip buffer */
 261
 262   /* Create the quantization buffer, if needed */
 263   if (cinfo->quantize_colors) {
 264     /* The buffer strip height is max_v_samp_factor, which is typically
 265      * an efficient number of rows for upsampling to return.
 266      * (In the presence of output rescaling, we might want to be smarter?)
 267      */
 268     post->strip_height = (JDIMENSION) cinfo->max_v_samp_factor;
 269     if (need_full_buffer) {
 270       /* Two-pass color quantization: need full-image storage. */
 271       /* We round up the number of rows to a multiple of the strip height. */
 272 #ifdef QUANT_2PASS_SUPPORTED
 273       post->whole_image = (*cinfo->mem->request_virt_sarray)
 274         ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
 275          cinfo->output_width * cinfo->out_color_components,
 276          (JDIMENSION) jround_up((long) cinfo->output_height,
 277                                 (long) post->strip_height),
 278          post->strip_height);
 279 #else
 280       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
 281 #endif /* QUANT_2PASS_SUPPORTED */
 282     } else {
 283       /* One-pass color quantization: just make a strip buffer. */
 284       post->buffer = (*cinfo->mem->alloc_sarray)
 285         ((j_common_ptr) cinfo, JPOOL_IMAGE,
 286          cinfo->output_width * cinfo->out_color_components,
 287          post->strip_height);
 288     }
 289   }
 290 }