rawIOsgi.cpp

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   5  * The MIT License
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   7  * Copyright (c) 2008 BBC Research
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  10  * of this software and associated documentation files (the "Software"), to deal
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  28
  29 //SGI file format header
  30 //      2 bytes | short  | MAGIC     | IRIS image file magic number
  31 //      1 byte  | char   | STORAGE   | Storage format,    0=VERBATIM, 1=RLE
  32 //      1 byte  | char   | BPC       | Number of bytes per pixel channel
  33 //      2 bytes | ushort | DIMENSION | Number of dimensions, 1=1 line of XSIZE; 2=1 plane of XSIZE*YSIZE (greyscale image); 3=ZSIZE planes of XSIZE*YSIZE (RGB image)
  34 //      2 bytes | ushort | XSIZE     | X size in pixels
  35 //      2 bytes | ushort | YSIZE     | Y size in pixels
  36 //      2 bytes | ushort | ZSIZE     | Number of channels
  37 //      4 bytes | long   | PIXMIN    | Minimum pixel value
  38 //      4 bytes | long   | PIXMAX    | Maximum pixel value
  39 //      4 bytes | char   | DUMMY     | Ignored
  40 //     80 bytes | char   | IMAGENAME | Image name
  41 //      4 bytes | long   | COLORMAP  | Colormap ID
  42 //    404 bytes | char   | DUMMY     | Ignored
  43
  44
  45 #define DEBUG 0
  46
  47 #include <assert.h>
  48
  49 #include "rawIOsgi.h"
  50
  51 //read a 16 bit value, endian safe
  52 inline unsigned short getshort(FILE *inf)
  53 {
  54         unsigned char buf[2];
  55
  56         fread(buf, 2, 1, inf);
  57         return (buf[0]<<8)+(buf[1]<<0);
  58 }
  59
  60 //read a 32 bit value, endian safe
  61 inline long getlong(FILE *inf)
  62 {
  63         unsigned char buf[4];
  64
  65         fread(buf, 4, 1, inf);
  66         return (buf[0]<<24)+(buf[1]<<16)+(buf[2]<<8)+(buf[3]<<0);
  67 }
  68
  69 void RawReadersgi::readHeader()
  70 {
  71         _magic = getshort(infile);
  72
  73         //bail out if this does not look like an SGI file
  74         if (_magic != 474)
  75                 return;
  76
  77         fread(&_storage, 1, 1, infile);
  78         fread(&_bpc, 1, 1, infile);
  79         _dimension = getshort(infile);
  80         _width = getshort(infile);
  81         _height = getshort(infile);
  82         _zsize = getshort(infile);
  83         _pixmin = getlong(infile);
  84         _pixmax = getlong(infile);
  85         fseek(infile, 4, SEEK_CUR); //skip dummy 4 bytes
  86         fread(&_name, 80, 1, infile); //80 bytes name
  87         _name[80]='\0'; //force string termination
  88         _colormap = getlong(infile);
  89         fseek(infile, 404, SEEK_CUR); //skip dummy 404 bytes
  90
  91         //set depth to 8 or 16 bits
  92         _depth=8;
  93         if (_bpc==2)
  94                 _depth=16;
  95
  96         //we are now 512 bytes into the file, which is the end of the header
  97         if (DEBUG) {
  98                 printf("MAGIC      = %d\n", _magic);
  99                 printf("STORAGE    = %d\n", _storage);
 100                 printf("BPC        = %d\n", _bpc);
 101                 printf("DIMENSIONS = %d\n", _dimension);
 102                 printf("XSIZE      = %d\n", _width);
 103                 printf("YSIZE      = %d\n", _height);
 104                 printf("ZSIZE      = %d\n", _zsize);
 105                 printf("PIXMIN     = %ld\n", _pixmin);
 106                 printf("PIXMAX     = %ld\n", _pixmax);
 107                 printf("NAME       = %s\n", _name);
 108                 printf("COLORMAP   = %ld\n", _colormap);
 109         }
 110 }
 111
 112 void RawReadersgi::read_plane(Array2d<int> &p, int ysize)
 113 {
 114         size_t linesRead;
 115         //note that the scan lines are stored in reverse order, bottom to top of frame
 116
 117
 118         switch (_bpc) {
 119         case 1:
 120         {
 121                 //8 bits per channel
 122                 unsigned char *inLine = new unsigned char[p.width()];
 123
 124                 for (int y=ysize-1; y>=0; y--) {
 125                         linesRead = fread(inLine, p.width(), 1, infile);
 126
 127                         for (int x = 0; x < p.width(); x++)
 128                                 p[y][x] = inLine[x];
 129
 130                         if (linesRead < 1)
 131                                 goto exit;
 132                 }
 133         }
 134                 break;
 135
 136         case 2:
 137         {
 138                 //16 bits per channel
 139                 unsigned char *inLine = new unsigned char[p.width()*2];
 140                 unsigned char *ptr;
 141                 for (int y=ysize-1; y>=0; y--) {
 142
 143                         linesRead = fread(inLine, p.width()*2, 1, infile);
 144                         ptr = inLine;
 145                         for (int x = 0; x < p.width(); x++, ptr+=2)
 146                                 p[y][x] = (ptr[0] << 8) | ptr[1];
 147
 148                         if (linesRead < 1)
 149                                 goto exit;
 150                 }
 151         }
 152                 break;
 153
 154         default:
 155                 break;
 156                 //undefined bpc
 157         }
 158
 159         exit: ;
 160
 161 }
 162
 163 RawFrame& RawReadersgi::read(RawFrame &f)
 164 {
 165         assert(f.chroma == RawFrame::CrRGB);
 166
 167         //we don't deal with run length coded files yet
 168         if (_storage != 0)
 169                 return f;
 170
 171         switch (_dimension) {
 172         case 1:
 173                 //there is one row of XSIZE pixels
 174                 read_plane(f.r, 1);
 175                 break;
 176
 177         case 2:
 178                 //there is one plane of XSIZE * YSIZE
 179                 read_plane(f.r, _height);
 180                 break;
 181
 182         case 3:
 183                 //there are ZSIZE planes of XSIZE * YSIZE
 184                 if (_zsize == 1) {
 185                         //greyscale
 186                         read_plane(f.r, _height);
 187                         f.g = f.r; //copy red plane to blue and green to get greyscale. Inefficient, but works
 188                         f.b = f.r;
 189                 }
 190
 191                 if (_zsize == 3 || _zsize == 4) {
 192                         //RGB or RGBA
 193                         read_plane(f.r, _height);
 194                         read_plane(f.g, _height);
 195                         read_plane(f.b, _height);
 196                 }
 197                 break;
 198         }
 199
 200         return f;
 201 }
 202
 203 RawFrame& RawReadersgi::read()
 204 {
 205         throw;
 206 }
 207