图像jpeg压缩算法介绍及其源码

/* *This progrmme is reedited from IJG code rdbmp.c by Fujian Shi(fieagle@yahoo.com). * This file and commondecls.h can finish a updown of a color bmp image. * */ #include "commondecls.h" /* Common decls for cjpeg/djpeg applications */ /* Macros to deal with unsigned chars as efficiently as compiler allows */ typedef unsigned char U_CHAR; #define UCH(x) ((int) (x)) #define JFREAD(file,buf,sizeofbuf) \ ((size_t) fread((void *) (buf), (size_t) 1, (size_t) (sizeofbuf), (file))) #define JFWRITE(file,buf,sizeofbuf) \ ((size_t) fwrite((const void *) (buf), (size_t) 1, (size_t) (sizeofbuf), (file))) #define ReadOK(file,buffer,len) (JFREAD(file,buffer,len) == ((size_t) (len))) #define WriteOK(file,buffer,len) (JFWRITE(file,buffer,len)==((size_t) (len))) #define LOCAL(type) static type /* Private version of data source object */ typedef struct _bmp_source_struct * bmp_source_ptr; typedef struct _bmp_source_struct { FILE *inputfile; /*source file pointer*/ FILE *outputfile; /*destination file pointer*/ JSAMPROW buffer; /*buffer pointer*/ JSAMPARRAY colormap; /* BMP colormap (converted to my format) */ UINT8 colormap_used; /*the tag of the colormap,in the real_color image,the colormap isn't used*/ JDIMENSION image_width; JDIMENSION image_height; /* BMP image height*/ /* Needed to reverse row order ,?reserved temply.*/ /*JDIMENSION source_row; Current source row number */ JDIMENSION row_width; /* Physical width of scanlines in file */ int bits_per_pixel; /* remembers 8- or 24-bit format */ UINT16 X_density ; /* 100 cm per meter */ UINT16 Y_density ; UINT8 density_unit ; /* dots/cm */ } bmp_source_struct; /*arrage a row buffer*/ LOCAL(void *) alloc_one_row(size_t size_object) { return (void *) malloc(size_object); } /*arrage several rows buffer,that is a array*/ LOCAL(JSAMPARRAY) alloc_sarray (JDIMENSION samplesperrow, JDIMENSION numrows) /* Allocate a 2-D sample array */ { JSAMPARRAY result; JSAMPROW workspace; int currow; /* Get space for row pointers (small object) */ result = (JSAMPARRAY) alloc_one_row((size_t) (numrows * SIZEOF(JSAMPROW))); /* Get the rows themselves (large objects) */ currow = 0; while (currow < numrows) { workspace = (JSAMPROW) alloc_one_row((size_t) (samplesperrow * SIZEOF(JSAMPLE))); result[currow++] = workspace; } return result; } LOCAL(int) read_byte (bmp_source_ptr sinfo) /* Read next byte from BMP file */ { register FILE *infile =sinfo->inputfile; register int c=0; if ((c = getc(infile)) == EOF){ printf("The wholefile has been input"); exit (0); } return c; } LOCAL(void) read_colormap (bmp_source_ptr sinfo, int cmaplen, int mapentrysize) /* Read the colormap from a BMP file */ /*cmalen is the number of color in the bmp image*/ { int i; switch (mapentrysize) { case 3: /* BGR format (occurs in OS/2 files) */ for (i = 0; i < cmaplen; i++) { sinfo->colormap[2][i] = (JSAMPLE) read_byte(sinfo); sinfo->colormap[1][i] = (JSAMPLE) read_byte(sinfo); sinfo->colormap[0][i] = (JSAMPLE) read_byte(sinfo); } break; case 4: /* BGR0 format (occurs in MS Windows files) */ for (i = 0; i < cmaplen; i++) { sinfo->colormap[2][i] = (JSAMPLE) read_byte(sinfo); sinfo->colormap[1][i] = (JSAMPLE) read_byte(sinfo); sinfo->colormap[0][i] = (JSAMPLE) read_byte(sinfo); (void) read_byte(sinfo); } break; default: exit (0); break; } } /* * Read one row of pixels. * The image has been read into the whole_image array, but is otherwise * unprocessed. We must read it out in top-to-bottom row order, and if * it is an 8-bit image, we must expand colormapped pixels to 24bit format. */ /*LOCAL(JDIMENSION) get_8bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo) *This version is for reading 8-bit colormap indexes* { bmp_source_ptr source = (bmp_source_ptr) sinfo; register JSAMPARRAY colormap = source->colormap; JSAMPARRAY image_ptr; register int t; register JSAMPROW inptr, outptr; register JDIMENSION col; * Fetch next row from virtual array * source->source_row--; image_ptr = (*cinfo->mem->access_virt_sarray) ((j_common_ptr) cinfo, source->whole_image, source->source_row, (JDIMENSION) 1, FALSE); * Expand the colormap indexes to real data * inptr = image_ptr[0]; outptr = source->pub.buffer[0]; for (col = cinfo->image_width; col > 0; col--) { t = GETJSAMPLE(*inptr++); *outptr++ = colormap[0][t]; * can omit GETJSAMPLE() safely * *outptr++ = colormap[1][t]; *outptr++ = colormap[2][t]; } return 1; } */ /*METHODDEF(JDIMENSION) get_24bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo) * This version is for reading 24-bit pixels * { bmp_source_ptr source = (bmp_source_ptr) sinfo; JSAMPARRAY image_ptr; register JSAMPROW inptr, outptr; register JDIMENSION col; * Fetch next row from virtual array * source->source_row--; image_ptr = (*cinfo->mem->access_virt_sarray) ((j_common_ptr) cinfo, source->whole_image, source->source_row, (JDIMENSION) 1, FALSE); * Transfer data. Note source values are in BGR order * (even though Microsoft's own documents say the opposite). * inptr = image_ptr[0]; outptr = source->pub.buffer[0]; for (col = cinfo->image_width; col > 0; col--) { outptr[2] = *inptr++; * can omit GETJSAMPLE() safely * outptr[1] = *inptr++; outptr[0] = *inptr++; outptr += 3; } return 1; } */ /* * This method loads the image into whole_image during the first call on * get_pixel_rows. The get_pixel_rows pointer is then adjusted to call * get_8bit_row or get_24bit_row on subsequent calls. */ LOCAL(JDIMENSION) process_image (bmp_source_ptr sinfo) { register FILE *infile = sinfo->inputfile; register FILE *outfile=sinfo->outputfile; register int c; register JSAMPROW buffer_ptr; /*buffer pointer,the buffer is only one row*/ JDIMENSION row, col; long position_adju; /* read and write data. */ for (row = 0; row < sinfo->image_height; row++) { buffer_ptr=sinfo->buffer; /*out_ptr = image_ptr[0];*/ for (col = sinfo->row_width; col > 0; col--) { /*by the cycle input one row sample into the buffer*/ /* inline copy of read_byte() for speed */ if ((c = getc(infile)) == EOF) exit(0); *buffer_ptr++ = (JSAMPLE) c; if(row==(sinfo->image_height-1)&&(col==2||col==1)) printf("the oribmp.bmp last pixel element is%d\n",c); } position_adju=(long) ((row+1)*sinfo->row_width); /*Whether it is need to add 2 depend on the image format, *normally it is 24 bit bmp image. */ fseek(outfile,-position_adju,SEEK_END); if(!WriteOK(outfile,sinfo->buffer,sinfo->row_width)){ printf("the data cann't be write into the new image.\n"); exit(0); } } /* Set up to read from the virtual array in top-to-bottom order * switch (sinfo->bits_per_pixel) { case 8: source->pub.get_pixel_rows = get_8bit_row; break; case 24: source->pub.get_pixel_rows = get_24bit_row; break; default: ERREXIT(cinfo, JERR_BMP_BADDEPTH); } source->source_row = cinfo->image_height; * And read the first row * return (*source->pub.get_pixel_rows) (cinfo, sinfo); */ } /* * Read the file header; return image size and component count. */ LOCAL(void) start_input_bmp (bmp_source_ptr sinfo) { U_CHAR bmpfileheader[14]; U_CHAR bmpinfoheader[64]; #define GET_2B(array,offset) ((unsigned int) UCH(array[offset]) + \ (((unsigned int) UCH(array[offset+1])) << 8)) #define GET_4B(array,offset) ((INT32) UCH(array[offset]) + \ (((INT32) UCH(array[offset+1])) << 8) + \ (((INT32) UCH(array[offset+2])) << 16) + \ (((INT32) UCH(array[offset+3])) << 24)) INT32 bfOffBits; INT32 headerSize; INT32 biWidt