jcapi.c

这是一个JPEG编码源代码

/* JPEG API Implemention File.
 */
#include <stdlib.h>
#include <mem.h>

#include "jinclude.h"

#include "jcapi.h"
#include "jcint.h"

/* Create a compress information object.
 */
jpeg_compress_info *
jpeg_create_compress( void ) 
{
  jpeg_compress_info *cinfo =
    (jpeg_compress_info *)malloc(sizeof(jpeg_compress_info));
    
  /* initialize all element to zero */
  memset((void *)(cinfo), 0, sizeof(jpeg_compress_info));
  cinfo->state = JC_CREATING;
  return cinfo;
}

/* Destory compress information object.
 */
void 
jpeg_destory_compress( jpeg_compress_info *cinfo ) {
  int i;
  
  if (cinfo->state != JC_FINISH)
    ;
  cinfo->state = JC_DESTORING;
  
  /* free */
  free(cinfo->inbuf);
  for (i=0; i<cinfo->num_comp; i++) {
    free(cinfo->comp[i].dct_table);
  }
  for (i=0; i<NUM_QUANT_TBLS; i++) {
    free(cinfo->quant_table[i]);
  }
  for (i=0; i<NUM_HUFF_TBLS; i++) {
    free(cinfo->dc_huff_table[i]);
    free(cinfo->ac_huff_table[i]);    
  }
  
  free(cinfo);
}

/* Set default value of jpeg compress. 
 * In our implemention we set Forward-DCT based JPEG Compress basic value.
 * Like : 8 (not 12) for precision or 3 for num_comp.
 * 
 * If you want use other Method of JPEG Compress, please set the cinfo self, 
 * not use this function. But don't forget invoke jpeg_calc_value to auto set, 
 * and initialize process buffer.
 */
void
jpeg_set_default( jpeg_compress_info *cinfo ) 
{
  cinfo->precision = 8;  
  cinfo->in_color_space = JCS_RGB;
  cinfo->quality = 0.65f;
  
  /* It's a good method to avoid foo code. */
  #define SET_COMP(TARGET,ID,H,V,Tq,Td,Ta) \
  ( TARGET.comp_id = (ID),\
    TARGET.comp_index = (ID),\
    TARGET.h_factor = (H),\
    TARGET.v_factor = (V),\
    TARGET.quant_tbl_no = (Tq),\
    TARGET.dc_tbl_no = (Td),\
    TARGET.ac_tbl_no = (Ta) )
  
  /* init color component, as YCbCr. */  
  cinfo->num_comp = 3;
  SET_COMP(cinfo->comp[0], 1, 2,2, 0, 0,0);
  SET_COMP(cinfo->comp[1], 2, 1,1, 1, 1,1);
  SET_COMP(cinfo->comp[2], 3, 1,1, 1, 1,1);
  
  /* set standrad quant tables */
  jint_std_quant_tables(cinfo);
  /* set standrad huffman tables */
  jint_std_huff_tables(cinfo);
  
  /* calc other value */
  jpeg_calc_value(cinfo);
}

/* Calculate some useful value and Alloc buffer memory.
 */
void 
jpeg_calc_value( jpeg_compress_info *cinfo ) 
{
  int i, h, v, bn;
  int size;
  jpeg_component_info *pcomp;
  
  /* AUTO set */
  cinfo->state = JC_SETTING;
  
  bn = 0;
  cinfo->max_h_factor = 0;
  cinfo->max_v_factor = 0;
  
  /* loop every component information 
   */
  for (i=0; i<cinfo->num_comp; i++) {
    pcomp = &cinfo->comp[i];
    h = pcomp->h_factor;
    v = pcomp->v_factor;
    
    if (cinfo->max_h_factor < h) {
      cinfo->max_h_factor = h;
    }
    if (cinfo->max_v_factor < v) {
      cinfo->max_v_factor = v;
    }
    bn += (h*v);
    
    /* WARMING ! 
       Malloc buffer here, but free it in jpeg_destory_compress() funtion. 
       So client must invoke it when finish compress. */
    pcomp->num_dct_table = h * v;
    size = sizeof(DCTBLOCK) * pcomp->num_dct_table;
    pcomp->dct_table = (DCTBLOCK *)malloc(size);
    memset((void *)(pcomp->dct_table), 0, size);
  }
  
  if (bn > MAX_BLOCK_IN_MCU) {
    /*~ err ~*/;
    exit(1);
  }
  
  cinfo->block_in_mcu = bn;
  cinfo->mcu_width  = cinfo->max_h_factor * DCTSIZE;
  cinfo->mcu_height = cinfo->max_v_factor * DCTSIZE;
  cinfo->mcu_blocks = cinfo->mcu_width * cinfo->mcu_height;
  
  /* set value about MCU 
   */
  cinfo->mcu_per_row = cinfo->image_width / cinfo->mcu_width;
  if (cinfo->image_width  % cinfo->mcu_width != 0)
    cinfo->mcu_per_row++;
  cinfo->mcu_rows    = cinfo->image_height / cinfo->mcu_height;
  if (cinfo->image_height % cinfo->mcu_height != 0)
    cinfo->mcu_rows++;
  
  /* set input buffer memory 
   */
  cinfo->inbuf_width  = cinfo->mcu_per_row * cinfo->mcu_width;
  cinfo->inbuf_height = cinfo->mcu_height;
  cinfo->inbuf_size = cinfo->inbuf_width * cinfo->inbuf_height 
                    * cinfo->num_comp  * sizeof(JSAMPLE);
  cinfo->inbuf = (JSAMPLE *)malloc( cinfo->inbuf_size);
  memset((void *)(cinfo->inbuf), 0, cinfo->inbuf_size);
  
  /* reset state value 
   */
  cinfo->next_line = 0;
}

/* Read image rows and compress.
 */
void 
jpeg_write_scanline( jpeg_compress_info *cinfo, 
                     JSAMPLE *samp_row ) 
{
  int x, c; /* for loop */
  int pos, size, last;
  int pos_s, pos_t, bsize;
  
  if (cinfo->state != JC_START) 
    exit(1);
  
  /* copy samp_row to color process buffer(cinfo->inbuf). 
   */
  size = cinfo->num_comp * sizeof(JSAMPLE);
  pos  = cinfo->inbuf_width * size * (cinfo->next_line % cinfo->inbuf_height);
  memcpy(&cinfo->inbuf[pos], samp_row, cinfo->image_width * size);

  /* full-filled buffer last-cols
   */
  last = cinfo->image_width - 1;
  pos += cinfo->image_width * size;
  for (x=0; x<cinfo->inbuf_width-cinfo->image_width; x++) {
    for (c=0; c<cinfo->num_comp; c++) {
      cinfo->inbuf[pos+x*cinfo->num_comp+c] = samp_row[last*cinfo->num_comp+c];
    }
  }/*
  last  = cinfo->image_width;
  bsize = cinfo->inbuf_width - cinfo->image_width;
  pos_s = pos + (cinfo->image_width - bsize)*size;
  pos_t = pos + last*size;
  memcpy(&cinfo->inbuf[pos_t], &cinfo->inbuf[pos_s], bsize*size);
  */
  cinfo->next_line++;
  
  
  
  /* When buffer full-filled we compress this data to output. */
  if (cinfo->next_line%cinfo->inbuf_height == 0) {
    /* Compress code here.
     */
    jint_process_rows(cinfo);
    memset((void *)(cinfo->inbuf), 0, cinfo->inbuf_size);
  }
}

/* Make compress start.
 * Write compress head to output.
 */
void
jpeg_start_compress  (jpeg_compress_info *cinfo) 
{
  int i;
  if (cinfo->state != JC_SETTING)
    exit(1);
  /* Add jpeg file heads , include file head & frame head & 
     scan head. */
  jmkr_write_start(cinfo);
  
  /* identify compress start */
  cinfo->state = JC_START;
  /* init stated-variable */
  cinfo->next_line = 0;
  for(i=0; i<cinfo->num_comp; i++) {
    cinfo->comp[i].preval = 0;
  }
}

/* Finish last compress. 
 * Compress last data in internal buffer & 
 * Write compress end-heads to output.
 */
void
jpeg_finish_compress (jpeg_compress_info *cinfo) 
{
  int i, startline, rowlen;
  JSAMPLE *data;
  if (cinfo->state != JC_START)
    exit(1);

  /* Finish compress data in cinfo->inbuf. */
  if (cinfo->next_line%cinfo->inbuf_height != 0) {
    rowlen = cinfo->inbuf_width * cinfo->num_comp * sizeof(JSAMPLE);
    startline = cinfo->next_line % cinfo->inbuf_height;
    data  = &cinfo->inbuf[(startline - 1)*rowlen];
    if (startline!=0) {
      for (i=startline; i<cinfo->inbuf_height; i++)
        memcpy(&cinfo->inbuf[i*rowlen], data,rowlen);
    }
    
    jint_process_rows(cinfo);  
  }

  jhuff_flush_buffer(cinfo); 
  /* Add jpeg file End-Heads . 
   * Free memory at jpeg_destroy_compress(cinfo). 
   */
  jmkr_write_end(cinfo);

  /* identify compress finish */
  cinfo->state = JC_FINISH;
}