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December 2004
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2004.12.07 11:57 "Re: Fetching pixel data from 4bit tiff", by Dan Field
> I'm not using the stuff myself, but it should indeed return R=G=B if the
> source is indeed grayscale. Perhaps we can see what's going on if you
> post a tagdump of the source tiff, and a code snippet. (A tagdump can be
> made with a tool included in LibTiff, tiffinfo, or by the tag viewer
> pointed to in my signature if you're a windows user.)
dof@nasty cropwill $ tiffinfo images/E0380040.tif
TIFF Directory at offset 0x8
Subfile Type: (0 = 0x0)
Image Width: 1735 Image Length: 3871
Resolution: 200, 200 pixels/inch
Bits/Sample: 4
Compression Scheme: None
Photometric Interpretation: min-is-white
Orientation: row 0 top, col 0 lhs
Samples/Pixel: 1
Rows/Strip: 3871
Planar Configuration: single image plane
Software: Pixel Translations Inc., PIXTIFF Version 54.2.210
Here's the code I've been writing.
Basically I'm trying to take a sample of pixels across the middle of the
image, both horizontal and vertical (yes I know the sample algo is wrong for
the horizontal.. I've yet to get to that :) )
// gnuplot settings
// set autoscale
// unset label
// set xtic auto
// set ytic auto
// set title "RGB Image Data for TIFF"
// set xlabel "Sampleline Pixels"
// set ylabel "Byte Value"
// plot "input.dat" using 0:1 title 'Red' smooth csplines , \
// "" using 0:2 title 'Green' smooth csplines , \
// "" using 0:3 title 'Blue' smooth csplines
// just set DEBUG = 1 and ./cropwill > ./test.dat to gain gnuplot input data
#define DEBUG
#define SUCCESS 1
#define SAMPLESIZE 100
#include <tiffio.h>
#include <stdio.h>
#include <stdlib.h>
typedef struct pixel {
int red;
int green;
int blue;
} Pixel;
typedef struct image {
char* name;
int width;
int height;
int size;
uint32 raster;
Pixel verticalSample[SAMPLESIZE];
Pixel horizontalSample[SAMPLESIZE];
} Image;
struct image TheImage;
void printImageInfo() {
printf("\n#########################################");
printf("\n# Filename: %s",TheImage.name);
printf("\n# Width: %i",TheImage.width);
printf("\n# Height: %i",TheImage.height);
printf("\n# Size: %i",TheImage.size);
printf("\n# Pixels: %i",TheImage.width * TheImage.height);
printf("\n#########################################\n");
}
TIFF* fetchImage(char* filename) {
TIFF* tif;
uint16 bps, spp;
if ((tif = TIFFOpen(filename, "r")) == NULL) {
printf("\nERROR: Could not open tif: %s.\n",filename);
exit (1);
}
if((TIFFGetField(tif, TIFFTAG_BITSPERSAMPLE, &bps) == 0) || (bps != 1)){
// fprintf(stderr, "Either undefined or unsupported number
of bits per sample\n");
TIFFSetField( tif, TIFFTAG_BITSPERSAMPLE, 4 );
/* exit(42); */
}
if((TIFFGetField(tif, TIFFTAG_SAMPLESPERPIXEL, &spp) == 0) || (spp != 1)){
fprintf(stderr, "Either undefined or unsupported number of
samples per pixel\n");
exit(42);
}
return tif;
}
unsigned long fetchRaster(TIFF* tif) {
uint32 w, h;
size_t npixels;
uint32* raster;
TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, &w);
TIFFGetField(tif, TIFFTAG_IMAGELENGTH, &h);
npixels = w * h;
TheImage.width = w;
TheImage.height = h;
raster = (uint32*) _TIFFmalloc(npixels * sizeof (uint32));
TheImage.size = npixels * sizeof (uint32);
TIFFReadRGBAImage(tif, w, h, raster, 0);
return *raster;
}
int main(int argc, char *argv[]) {
char *filename;
TIFF* tif;
uint32 raster, row;
tdata_t buf;
/* uint32 row; */
tsample_t s;
unsigned int i, vert_size, horiz_size, index;
unsigned int *vert, *horiz;
unsigned char R,G,B,A;
char already_allocated_string[255];
if (argc == 2) {
filename = argv[1];
TheImage.name = filename;
} else {
printf("\nERROR: Incorrect number of arguments to
cropwill.\n");
exit(1);
}
tif = fetchImage(filename);
if (tif == NULL) {
printf("\nERROR: NULL tiff returned\n");
exit(1);
}
raster = fetchRaster(tif);
TheImage.raster = raster;
#ifdef DEBUG
printImageInfo();
#endif
vert_size = (int)((float)TheImage.height/2.0);
horiz_size = (int)((float)TheImage.width/2.0);
vert = malloc(vert_size * sizeof(unsigned int));
horiz = malloc(horiz_size * sizeof(unsigned int));
index = 0;
for (i =TheImage.width/2; i < (TheImage.width*TheImage.height); i += TheImage.width) {
R=(unsigned char)TIFFGetR(raster+i);
G=(unsigned char)TIFFGetG(raster+i);
B=(unsigned char)TIFFGetB(raster+i);
A=(unsigned char)TIFFGetA(raster+i);
vert[index] = (unsigned int)(R+G+B);
#ifdef DEBUG
/* print out gnuplot data */
printf("%i\t%i\t%i\t%i\n", R, G, B, (R+G+B));
#endif
index++;
}
free(vert);
index = 0;
for (i = (((TheImage.width*TheImage.height)/2)-(TheImage.width/2));
i < (((TheImage.width*TheImage.height)/2)); i ++) {
R=(unsigned char)TIFFGetR(raster+i);
G=(unsigned char)TIFFGetG(raster+i);
B=(unsigned char)TIFFGetB(raster+i);
A=(unsigned char)TIFFGetA(raster+i);
horiz[index] = (unsigned int)(R+G+B);
//printf("h: %i\n",horiz[index]);
index++;
}
// free(horiz);
TIFFClose(tif);
return SUCCESS;
}
--
Dan Field <dof@llgc.org.uk> http://www.cymruarywe.org/
http://www.walesontheweb.org/
Developer / Sysadmin
Llyfyrgell Genedlaethol Cymru