LibTiff Mailing List
TIFF and LibTiff Mailing List Archive
July 2009
Previous Thread
Next Thread
Previous by Thread
Next by Thread
Previous by Date
Next by Date
Contact
The TIFF Mailing List Homepage
This list is run by Frank Warmerdam
Archive maintained by AWare Systems
Thread
2009.07.17 17:28 "Re: reading an 8 bit image", by Michael Persons
I just glanced at it and at first glance it appears that you would need to
increment the "ptr" variable by 4 and not by 3 since the image is a RGBA
image.
________________________________
From: tiff-bounces@lists.maptools.org
[mailto:tiff-bounces@lists.maptools.org] On Behalf Of Joe Tracy
Sent: Thursday, July 16, 2009 7:33 AM
To: tiff@lists.maptools.org
Subject: [Tiff] reading an 8 bit image
Hi,
I have been reading 16 bit grayscale tiff images for a while now using the
ReadScanLine method: this works fine.
However, I am unable to figure out how to read in an 8 bit image. I have
tried many variations, but the closest I come is this:
(I am just putting the pixel data into an array, then subsequently create an
image later. Using this method, my image is not correct.)
I am using C#.Net, using DLLImports for the libtiff calls.
TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, ref w);
TIFFGetField(tif, TIFFTAG_IMAGELENGTH, ref h);
TIFFGetField(tif, TIFFTAG_BITSPERSAMPLE, ref bits);
TIFFGetField(tif, TIFFTAG_SAMPLESPERPIXEL, ref
samples);
pixel_array = new int[h, w, 3];
UInt32 size = h * w;
byte* raster = _TIFFmalloc((UInt32)(size *
sizeof(UInt32)));
int val = TIFFReadRGBAImage(tif, w, h,
(byte*)raster, 0);
if (val != 0)
{
for (int j = 0; j < h; j++)
{
for (int i = 0, ptr = 0; i < w; i++, ptr
+= 3)
{
pixel_array[j, i, 0] =
(int)raster[ptr + j * w];
pixel_array[j, i, 1] =
(int)raster[ptr + 1 + j * w];
pixel_array[j, i, 2] =
(int)raster[ptr + 2 + j * w];
}
}
}
_TIFFfree((byte*)raster);
My image comes in "garbled". It is close, but not there.
Any help is appreciated.
Thanks,
Joe