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#charset utf-8 
#pike __REAL_VERSION__ 
 
//   Imagedimensionreadermodule for Pike. 
//   Created by Johan Sch´┐Żn, <js@roxen.com>. 
// 
//   This software is based in part on the work of the Independent JPEG Group. 
 
//! @appears Image.Dims 
//! Reads the dimensions of images of various image formats without 
//! decoding the actual image. 
 
#define M_SOF0  0xC0          /* Start Of Frame N */ 
#define M_SOF1  0xC1                /* N indicates which compression process */ 
#define M_SOF2  0xC2                /* Only SOF0-SOF2 are now in common use */ 
#define M_SOF3  0xC3 
#define M_SOF5  0xC5                /* NB: codes C4 and CC are NOT SOF markers */ 
#define M_SOF6  0xC6 
#define M_SOF7  0xC7 
#define M_SOF9  0xC9 
#define M_SOF10 0xCA 
#define M_SOF11 0xCB 
#define M_SOF13 0xCD 
#define M_SOF14 0xCE 
#define M_SOF15 0xCF 
#define M_SOI   0xD8                /* Start Of Image (beginning of datastream) */ 
#define M_EOI   0xD9                /* End Of Image (end of datastream) */ 
#define M_SOS   0xDA                /* Start Of Scan (begins compressed data) */ 
#define M_COM   0xFE                /* COMment */ 
#define M_APP1  0xE1 
 
protected int(0..255) read_1_byte(Stdio.File f) 
{ 
  return f->read(1)[0]; 
} 
 
protected int(0..65535) read_2_bytes(Stdio.File f) 
{ 
  int c; 
  sscanf( f->read(2), "%2c", c ); 
  return c; 
} 
 
 
/* 
 * Read the initial marker, which should be SOI. 
 * For a JFIF file, the first two bytes of the file should be literally 
 * 0xFF M_SOI.  To be more general, we could use next_marker, but if the 
 * input file weren't actually JPEG at all, next_marker might read the whole 
 * file and then return a misleading error message... 
 */ 
 
protected int first_marker(Stdio.File f) 
{ 
  int c1, c2; 
 
  sscanf(f->read(2), "%c%c", c1, c2); 
  if (c1==0xFF||c2==M_SOI) return 1; 
  return 0; 
} 
 
/* 
 * Find the next JPEG marker and return its marker code. 
 * We expect at least one FF byte, possibly more if the compressor used FFs 
 * to pad the file. 
 * There could also be non-FF garbage between markers.  The treatment of such 
 * garbage is unspecified; we choose to skip over it but emit a warning msg. 
 * NB: this routine must not be used after seeing SOS marker, since it will 
 * not deal correctly with FF/00 sequences in the compressed image data... 
 */ 
 
protected int next_marker(Stdio.File f) 
{ 
  // Find 0xFF byte; count and skip any non-FFs. 
  int c = read_1_byte(f); 
  while (c != 0xFF) 
    c = read_1_byte(f); 
 
  // Get marker code byte, swallowing any duplicate FF bytes.  Extra FFs 
  // are legal as pad bytes. 
  do { 
    c = read_1_byte(f); 
  } while (c == 0xFF); 
  return c; 
} 
 
/* Skip over an unknown or uninteresting variable-length marker */ 
protected int skip_variable(Stdio.File f) 
{ 
  int length = read_2_bytes(f); 
  if (length < 2) return 0;  // Length includes itself, so must be at least 2. 
  length -= 2; 
  f->seek(length, Stdio.SEEK_CUR); 
  return 1; 
} 
 
//! Reads the dimensions from a JPEG file and returns an array with 
//! width and height, or if the file isn't a valid image, 0. 
array(int) get_JPEG(Stdio.File f) 
{ 
  if (!first_marker(f)) 
    return 0; 
 
  mapping exif; 
 
  /* Scan miscellaneous markers until we reach SOS. */ 
  for (;;) 
  { 
    switch (next_marker(f)) { 
    case M_SOF0:            /* Baseline */ 
    case M_SOF1:            /* Extended sequential, Huffman */ 
    case M_SOF2:            /* Progressive, Huffman */ 
    case M_SOF3:            /* Lossless, Huffman */ 
    case M_SOF5:            /* Differential sequential, Huffman */ 
    case M_SOF6:            /* Differential progressive, Huffman */ 
    case M_SOF7:            /* Differential lossless, Huffman */ 
    case M_SOF9:            /* Extended sequential, arithmetic */ 
    case M_SOF10:           /* Progressive, arithmetic */ 
    case M_SOF11:           /* Lossless, arithmetic */ 
    case M_SOF13:           /* Differential sequential, arithmetic */ 
    case M_SOF14:           /* Differential progressive, arithmetic */ 
    case M_SOF15:           /* Differential lossless, arithmetic */ 
      int image_height, image_width; 
      sscanf(f->read(7), "%*3s%2c%2c", image_height, image_width); 
      if( exif && has_value(exif, "Orientation") && 
          (< "5", "6", "7", "8" >)[exif->Orientation] ) 
      { 
        // Picture has been rotated/flipped 90 or 270 degrees, so 
        // exchange width and height to reflect that. 
        int tmp = image_height; 
        image_height = image_width; 
        image_width = tmp; 
      } 
      return ({ image_width,image_height }); 
      break; 
 
    case M_APP1: 
      int pos = f->tell(); 
      f->seek(pos-2); 
      catch { 
        exif = Standards.EXIF.get_properties(f, ([ 0x0112 : 
                                                   ({ "Orientation" }) ])); 
      }; 
      f->seek(pos); 
      if(!skip_variable(f)) return 0; 
      break; 
 
    case M_SOS:                     /* stop before hitting compressed data */ 
      return 0; 
 
    case M_EOI:                     /* in case it's a tables-only JPEG stream */ 
      return 0; 
 
    default:                        /* Anything else just gets skipped */ 
      if(!skip_variable(f)) return 0; // we assume it has a parameter count... 
      break; 
    } 
  } 
} 
 
// GIF-header: 
// typedef struct _GifHeader 
// { 
//   // Header 
//   BYTE Signature[3];     /* Header Signature (always "GIF") */ 
//   BYTE Version[3];       /* GIF format version("87a" or "89a") */ 
//   // Logical Screen Descriptor 
//   WORD ScreenWidth;      /* Width of Display Screen in Pixels */ 
//   WORD ScreenHeight;     /* Height of Display Screen in Pixels */ 
//   BYTE Packed;           /* Screen and Color Map Information */ 
//   BYTE BackgroundColor;  /* Background Color Index */ 
//   BYTE AspectRatio;      /* Pixel Aspect Ratio */ 
// } GIFHEAD; 
 
//! Reads the dimensions from a GIF file and returns an array with 
//! width and height, or if the file isn't a valid image, 0. 
array(int) get_GIF(Stdio.File f) 
{ 
  if(f->read(3)!="GIF") return 0; 
  f->seek(3, Stdio.SEEK_CUR); 
  return array_sscanf(f->read(4), "%-2c%-2c"); 
} 
 
//! Reads the dimensions from a PNG file and returns an array with 
//! width and height, or if the file isn't a valid image, 0. 
array(int) get_PNG(Stdio.File f) 
{ 
  int offs=f->tell(); 
  if(f->read(6)!="\211PNG\r\n") return 0; 
  f->seek(6, Stdio.SEEK_CUR); 
  if(f->read(4)!="IHDR") return 0; 
  return array_sscanf(f->read(8), "%4c%4c"); 
} 
 
//! Reads the dimensions from a TIFF file and returns an array with 
//! width and height, or if the file isn't a valid image, 0. 
array(int) get_TIFF(Stdio.File f) 
{ 
 int|string buf; 
 int entries; 
 int val = 0; 
 string bo2b; 
 string bo4b; 
 
 buf = f->read(2); 
 if(buf == "II") 
 { 
   /* Byte order for Little endian */ 
   bo2b = "%2-c"; 
   bo4b = "%4-c"; 
 } 
 else if(buf == "MM") 
 { 
   /* Byte order for Big endian */ 
   bo2b = "%2c"; 
   bo4b = "%4c"; 
 } 
 else 
 { 
   /* Not a TIFF */ 
   return 0; 
 } 
 
 sscanf(f->read(2), bo2b, buf); 
 if(buf != 42) 
 { 
   /* Wrong magic number */ 
   return 0; 
 } 
 
 /* offset to first IFD */ 
 sscanf(f->read(4), bo4b, buf); 
 f->seek(buf); 
 
 /* number of entries */ 
 sscanf(f->read(2), bo2b, entries); 
 
 for(int i = 0; i < entries; i++) 
 { 
   sscanf(f->read(2), bo2b, int tag); 
   if(tag == 256 || tag == 257) 
   { 
     sscanf(f->read(2), bo2b, buf); 
     /* Count value must be one(1) */ 
     sscanf(f->read(4), bo4b, int count); 
     if(count == 1) 
     { 
       if(buf == 3) 
       { 
         /* Type short */ 
         sscanf(f->read(2), bo2b, buf); 
         /* Skip to the end of the entry */ 
         f->seek(2, Stdio.SEEK_CUR); 
       } 
       else if(buf == 4) 
       { 
         /* Type long */ 
         sscanf(f->read(4), bo4b, buf); 
       } 
       else 
       { 
         /* Wrong type */ 
         return 0; 
       } 
 
       if(tag == 256) 
       { 
         /* ImageWidth */ 
         if(val == 0) 
           val = buf; 
         else 
           return ({buf, val}); 
       } 
       else 
       { 
         /* ImageLength */ 
         if(val == 0) 
           val = buf; 
         else 
           return ({val, buf}); 
       } 
     } 
     else 
     { 
       /* Wrong count value */ 
       return 0; 
     } 
   } 
   else 
   { 
     /* Skip to next entry */ 
     f->seek(10, Stdio.SEEK_CUR); 
   } 
 } 
 /* ImageWidth and ImageLength not found */ 
 return 0; 
} 
 
//! Reads the dimensions from a PSD file and returns an array with 
//! width and height, or if the file isn't a valid image, 0. 
array(int) get_PSD(Stdio.File f) 
{ 
  //  4 bytes signature + 2 bytes version 
  if (f->read(6) != "8BPS\0\1") return 0; 
 
  //  6 bytes reserved 
  //  2 bytes channel count 
  f->read(8); 
 
  //  4 bytes height, 4 bytes width (big-endian) 
  return reverse(array_sscanf(f->read(8), "%4c%4c")); 
} 
 
//! Reads the dimensions from a WebP file and returns an array with 
//! width and height, or if the file isn't a valid image, 0. 
array(int) get_WebP(Stdio.File f) 
{ 
  if (f->read(4) != "RIFF") return 0; 
  f->read(4); 
  if (f->read(4) != "WEBP") return 0; 
 
  switch(f->read(4)) 
  { 
  case "VP8 ": 
    /* Lossy coding */ 
    f->read(4); // Size of chunk. Not in Google documentation. 
    f->read(3); // Frame tag. 
    if(f->read(3)!="\x9d\x01\x2a") return 0; 
    // Ignore the scaling factor, as it is upscaling and not actual 
    // image information. 
    return array_sscanf(f->read(4), "%-2c%-2c")[*] & 0x3fff; 
    break; 
  case "VP8L": 
    /* Lossless coding */ 
    f->read(4); 
    if( f->read(1) != "/" ) return 0; 
 
    string data = f->read(4); 
    int width = (data[0] | (data[1] & 0x3f)<<8) + 1; 
    int height = (data[1]>>6 | data[2]<<2 | (data[3] & 0x0f)<<10) + 1; 
    return ({ width, height }); 
    break; 
  case "VP8X": 
    /* Extended VP8 */ 
    f->read(4); 
    f->read(4); // flags and reserved 
    return array_sscanf(f->read(6), "%-3c%-3c")[*]+1; 
    break; 
  } 
  return 0; 
} 
 
//! Read dimensions from a JPEG, GIF, PNG, WebP, TIFF or PSD file and 
//! return an array with width and height, or if the file isn't a 
//! valid image, @expr{0@}. The argument @[file] should be file object 
//! or the data from a file. The offset pointer will be assumed to be 
//! at the start of the file data and will be modified by the 
//! function. 
//! 
//! @returns 
//!   @array 
//!     @elem int 0 
//!       Image width. 
//!     @elem int 1 
//!       Image height. 
//!     @elem string 2 
//!       Image type. Any of @expr{"gif"@}, @expr{"png"@}, @expr{"tiff"@}, 
//!       @expr{"jpeg"@}, @expr{"webp"@} and @expr{"psd"@}. 
//!   @endarray 
array(int|string) get(string|Stdio.File file) { 
 
  if(stringp(file)) 
    file = Stdio.FakeFile(file); 
 
  array ret; 
  switch(file->read(2)) 
  { 
  case "GI": 
    if( (< "F87a", "F89a" >)[file->read(4)] ) 
      return array_sscanf(file->read(4), "%-2c%-2c") + ({ "gif" }); 
    break; 
 
  case "\x89P": 
    if(file->read(4)=="NG\r\n") 
    { 
      file->read(6+4); 
      return array_sscanf(file->read(8), "%4c%4c") + ({ "png" }); 
    } 
    break; 
 
  case "8B": 
    if(file->read(4)=="PS\0\1") 
    { 
      file->read(6+2); 
      return reverse(array_sscanf(file->read(8), "%4c%4c")) + ({ "psd" }); 
    } 
    break; 
 
  case "II": 
  case "MM": 
    file->seek(-2, Stdio.SEEK_CUR); 
    ret = get_TIFF(file); 
    if(ret) return ret+({ "tiff" }); 
    break; 
 
  case "\xff\xd8": 
    file->seek(-2, Stdio.SEEK_CUR); 
    ret = get_JPEG(file); 
    if(ret) return ret+({ "jpeg" }); 
    break; 
 
  case "RI": 
    file->seek(-2, Stdio.SEEK_CUR); 
    ret = get_WebP(file); 
    if(ret) return ret+({ "webp" }); 
    break; 
  } 
 
  return 0; 
}