用 libtiff 进行图形编程，第 2 部分

#include <tiffio.h>
#include <stdio.h>
int main(int argc, char *argv[]){
  TIFF *output;
  uint32 width, height;
  char *raster;
  // Open the output image
  if((output = TIFFOpen("output.tif", "w")) == NULL){
    fprintf(stderr, "Could not open outgoing image\n");
    exit(42);
  }
  // We need to know the width and the height before we can malloc
  width = 42;
  height = 42;
  if((raster = (char *) malloc(sizeof(char) * width * height * 3)) == NULL){
    fprintf(stderr, "Could not allocate enough memory\n");
    exit(42);
  }
  // Magical stuff for creating the image
  // ...
  // Write the tiff tags to the file
  TIFFSetField(output, TIFFTAG_IMAGEWIDTH, width);
  TIFFSetField(output, TIFFTAG_IMAGELENGTH, height);
  TIFFSetField(output, TIFFTAG_COMPRESSION, COMPRESSION_DEFLATE);
  TIFFSetField(output, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
  TIFFSetField(output, TIFFTAG_PHOTOMETRIC, PHOTOMETRIC_RGB);
  TIFFSetField(output, TIFFTAG_BITSPERSAMPLE, 8);
  TIFFSetField(output, TIFFTAG_SAMPLESPERPIXEL, 3);
  // Actually write the image
  if(TIFFWriteEncodedStrip(output, 0, raster, width * height * 3) == 0){
    fprintf(stderr, "Could not write image\n");
    exit(42);
  }
  TIFFClose(output);
}

   TIFFReadRGBAStrip reads a single strip of a strip-based image into memory,
   storing  the  result  in  the  user supplied RGBA raster. The raster is
   assumed to be an array of width times   rowsperstrip   32-bit   entries,
   where   width   is  the  width  of  the  image (TIFFTAG_IMAGEWIDTH) and
   rowsperstrip is the maximum lines in a strip (TIFFTAG_ROWSPERSTRIP).
   The  strip  value  should  be  the  strip  number  (strip  zero  is the
   first) as returned by the TIFFComputeStrip function, but always for sample 0.
   Note  that  the  raster  is  assume  to  be  organized  such  that the pixel
   at location (x,y) is raster[y*width+x];  with  the  raster  origin in the
   lower-left hand corner of the strip. That is bottom  to  top  organization.
   When reading a partial last strip in the file the last line of the image
   will begin at the beginning of the buffer.
   Raster  pixels  are  8-bit packed red, green, blue, alpha samples. The
   macros TIFFGetR, TIFFGetG, TIFFGetB,  and  TIFFGetA  should  be used to
   access individual samples. Images without Associated Alpha matting
   information have a constant Alpha of 1.0 (255).
   See  the TIFFRGBAImage(3T) page for more details on how various image types
   are converted to RGBA values.
NOTES
   Samples must be either 1, 2, 4, 8, or 16 bits. Colorimetric samples/pixel
   must be either 1, 3, or 4 (i.e. SamplesPerPixel minus ExtraSamples).
   Palette  image  colormaps that appear to be incorrectly written as 8-bit
   values are automatically scaled to 16-bits.
   TIFFReadRGBAStrip  is  just  a wrapper around the more general
   TIFFRGBAImage(3T) facilities. It's main  advantage  over  the similar
   TIFFReadRGBAImage() function is that for large images a single buffer
   capable  of  holding  the  whole  image doesn't need to be allocated, only
   enough for one strip. The TIFFReadRGBATile() function does a similar
   operation for tiled images.

#include <stdio.h>
#include <tiffio.h>
int main(int argc, char *argv[]){
  TIFF *image;
  uint32 width, height, *raster;
  tsize_t stripSize;
  unsigned long imagesize, c, d, e;
  // Open the TIFF image
  if((image = TIFFOpen(argv[1], "r")) == NULL){
    fprintf(stderr, "Could not open incoming image\n");
    exit(42);
  }
  // Find the width and height of the image
  TIFFGetField(image, TIFFTAG_IMAGEWIDTH, &width);
  TIFFGetField(image, TIFFTAG_IMAGELENGTH, &height);
  imagesize = height * width + 1;
  
  if((raster = (uint32 *) malloc(sizeof(uint32) * imagesize)) == NULL){
    fprintf(stderr, "Could not allocate enough memory\n");
    exit(42);
  }
  // Read the image into the memory buffer
  if(TIFFReadRGBAStrip(image, 0, raster) == 0){
    fprintf(stderr, "Could not read image\n");
    exit(42);
  }
// Here I fix the reversal of the image (vertically) and show you
// how to get the color values from each pixel
  d = 0;
  for(e = height - 1; e != -1; e--){
    for(c = 0; c < width; c++){
      // Red = TIFFGetR(raster[e * width + c]);
      // Green = TIFFGetG(raster[e * width + c]);
      // Blue = TIFFGetB(raster[e * width + c]);
    }
  }
  free(raster);
  TIFFClose(image);
}

#include <tiffio.h>
#include <pthread.h>
// Function prototypes
static tsize_t libtiffDummyReadProc (thandle_t fd, tdata_t buf, tsize_t size);
static tsize_t libtiffDummyWriteProc (thandle_t fd, tdata_t buf, tsize_t size);
static toff_t libtiffDummySeekProc (thandle_t fd, toff_t off, int i);
static int libtiffDummyCloseProc (thandle_t fd);
// We need globals because of the callbacks (they don't allow us to pass state)
char *globalImageBuffer;
unsigned long globalImageBufferOffset;
// This mutex keeps the globals safe by ensuring only one user at a time
pthread_mutex_t convMutex = PTHREAD_MUTEX_INITIALIZER;
...
TIFF *conv;
// Lock the mutex
pthread_mutex_lock (&convMutex);
globalImageBuffer = NULL;
globalImageBufferOffset = 0;
// Open the dummy document (which actually only exists in memory)
conv = TIFFClientOpen ("dummy", "w", (thandle_t) - 1, libtiffDummyReadProc,
            libtiffDummyWriteProc, libtiffDummySeekProc,
            libtiffDummyCloseProc, NULL, NULL, NULL);
// Setup the image as if it was any other tiff image here, including setting tags
...
// Actually do the client open
TIFFWriteEncodedStrip (conv, 0, stripBuffer, imageOffset);
// Unlock the mutex
pthread_mutex_unlock (&convMutex);
...
/////////////////// Callbacks to libtiff
...
static tsize_t
libtiffDummyReadProc (thandle_t fd, tdata_t buf, tsize_t size)
{
  // Return the amount of data read, which we will always set as 0 because
  // we only need to be able to write to these in-memory tiffs
  return 0;
}
static tsize_t
libtiffDummyWriteProc (thandle_t fd, tdata_t buf, tsize_t size)
{
  // libtiff will try to write an 8 byte header into the tiff file. We need
  // to ignore this because PDF does not use it...
  if ((size == 8) && (((char *) buf)[0] == 'I') && (((char *) buf)[1] == 'I')
     && (((char *) buf)[2] == 42))
    {
    // Skip the header -- little endian
    }
  else if ((size == 8) && (((char *) buf)[0] == 'M') &&
       (((char *) buf)[1] == 'M') && (((char *) buf)[2] == 42))
    {
    // Skip the header -- big endian
    }
  else
    {
    // Have we done anything yet?
    if (globalImageBuffer == NULL)
    if((globalImageBuffer = (char *) malloc (size * sizeof (char))) == NULL)
        {
          fprintf(stderr, "Memory allocation error\n");
          exit(42);
        }
    // Otherwise, we need to grow the memory buffer
    else
    {
      if ((globalImageBuffer = (char *) realloc (globalImageBuffer,
                             (size * sizeof (char)) +
                             globalImageBufferOffset)) == NULL)
        fprintf(stderr, "Could not grow the tiff conversion memory buffer\n");
            exit(42);
    }
    // Now move the image data into the buffer
    memcpy (globalImageBuffer + globalImageBufferOffset, buf, size);
    globalImageBufferOffset += size;
    }
  return (size);
}
static toff_t
libtiffDummySeekProc (thandle_t fd, toff_t off, int i)
{
  // This appears to return the location that it went to
  return off;
}
static int
libtiffDummyCloseProc (thandle_t fd)
{
  // Return a zero meaning all is well
  return 0;
}