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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 }
    291