Read large TIFF file into float array for CUDA

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi All,

I am having an issue reading a TIFF file into a float array to ‘feed’ into my CUDA coda for image processing.

Is there any way that this can be done using CUDA? I can get the TIFF data into a BYTE array no problem but from there I am not having much luck.

I am using VC++.

Any help will be appreciated.

Thanks in advance.

AK

2

Load it as bytes, pass it likewise to CUDA kernel and convert any sample You take to float, before doing other operations.

MK

3

Hi MK,

Thank you very much for the response. Much appreciated. How would I go about doing the conversion from bytes to float in CUDA and vise verse from float to bytes after the rotation?

Thanks in advance.

AK

4

Hi,
You’ll need to know how many bytes there is per pixel, or even per pixel channel (R, G, B at least). You’ll also need to know how they are ordered within a pixel, in other words are they RGB, BGR or GBR etc. This stuff You’ll know form TIFF format specification.

CUDA code making the conversion is henceforth simple - take the appropiate number of bytes that is per pixel channel (usually a sizeof(unsigned char) == 1 byte per channel), devide it as float by the max number that there can be stored with the number of bytes plus 1 (1 byte means the max number is 255, +1 equals 256) and finally store such number in an appropiate float4 (or float3 provided there is no alpha channel) vector (R goes to X, G goes to Y, B goes to Z and A goes to W).

The other-way-conversion differs only with the fact that instead a float division You perform a multiplication.

A hopefully helpful pseudo-code below:

// Byte to float
byte2float(b,f) {
  f[X] = ((float)b[R] / 256.0f);
  f[Y] = ((float)b[G] / 256.0f);
  f[Z] = ((float)b[B] / 256.0f);
  f[W] = ((float)b[A] / 256.0f);
}

// Float to byte
float2byte(f,b) {
  b[R] = (byte)(f[R] * 256.0f);
  b[G] = (byte)(f[G] * 256.0f);
  b[B] = (byte)(f[B] * 256.0f);
  b[A] = (byte)(f[A] * 256.0f);
}

Cheers,
MK

5

Hi MK,

Sorry for the late response. Thank you very much! I will try this out as soon as I can and advise.

Thanks,

AK

6

If you just want to read tiff files,i’d like to suggest you create a tiff viewer
,which can read tiff and process tiff files.