I am trying to solve a problem in which i am supposed to change a colour image to a greyscale image. For this purpose i am using CUDA parallel approach.
The kerne code i
const dim3 blockSize(16, 16, 1); //TODO
const dim3 gridSize( (numRows+15)/16, (numCols+15)/16, 1); //TODO
int x = blockIdx.x * blockDim.x + threadIdx.x;
int y = blockIdx.y * blockDim.y + threadIdx.y;
uchar4 rgba = rgbaImage[y*numRows + x];
float channelSum = .299f * rgba.x + .587f * rgba.y + .114f * rgba.z;
greyImage[y*numRows + x] = channelSum;
the calculation of absolute x & y image positions is perfect. but when u need to access that particular pixel in the coloured image , shouldn't you u use the following code??
uchar4 rgba = rgbaImage[absolute_image_position_x + (absolute_image_position_y * numCols)];
I thought so, when comparing it to a code you'd write to execute the same problem in serial code. Please let me know :)
same code with with ability to handle non-standard input size images
int idx=blockDim.x*blockIdx.x+threadIdx.x;
int idy=blockDim.y*blockIdx.y+threadIdx.y;
uchar4 rgbcell=rgbaImage[idx*numCols+idy];
greyImage[idx*numCols+idy]=0.299*rgbcell.x+0.587*rgbcell.y+0.114*rgbcell.z;
}
void your_rgba_to_greyscale(const uchar4 * const h_rgbaImage, uchar4 * const d_rgbaImage,
unsigned char* const d_greyImage, size_t numRows, size_t numCols)
{
//You must fill in the correct sizes for the blockSize and gridSize
//currently only one block with one thread is being launched
int totalpixels=numRows*numCols;
int factors[]={2,4,8,16,24,32};
vector<int> numbers(factors,factors+sizeof(factors)/sizeof(int));
int factor=1;
while(!numbers.empty())
{
if(totalpixels%numbers.back()==0)
{
factor=numbers.back();
break;
}
else
{
numbers.pop_back();
}
}
const dim3 blockSize(factor, factor, 1); //TODO
const dim3 gridSize(numRows/factor+1, numCols/factor+1,1); //TODO
rgba_to_greyscale<<<gridSize, blockSize>>>(d_rgbaImage, d_greyImage, numRows, numCols);
libdc1394 error: Failed to initialize libdc1394
I don't think that this is a CUDA problem. libdc1394 is a library used to access IEEE1394 aka FireWire aka iLink video devices (DV camcorders, Apple iSight camera). That library doesn'r properly initialize, hence you're not getting usefull results. Basically it's NINO: Nonsens In Nonsens Out.
You still should have a problem with run time - the conversion will not give a proper result.
The lines:
should be changed to:
The libdc1394 error is not related to firewire etc in this case - it is the library that udacity is using to compare the image your program creates to the reference image. And what is is saying is that the difference between your image and the reference image has been been exceeded by a specific threshold, for that position ie. pixel.