rgba_to_greyscale.cu

#include "reference_calc.cpp"
#include "utils.h"
#include <stdio.h>

__global__
void rgba_to_greyscale(const uchar4* const rgbaImage,
                       unsigned char* const greyImage,
                       int numRows, int numCols)
{

 int i = blockIdx.x * blockDim.x + threadIdx.x;// determina iteração das linhas
 int j =blockIdx.y * blockDim.y + threadIdx.y; //determina iteração das colunas
    if(i<numRows && j< numCols){
            uchar4 rgba = rgbaImage[i*numCols + j];
            float channelSum = .299f * rgba.x + .587f * rgba.y + .114f * rgba.z;
            greyImage[i*numCols +j]= channelSum;
        
    }
    
    
}

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)
{
  int blockWidth = 32;//Determino qual tamanho de bloco usar
  const dim3 blockSize(blockWidth, blockWidth, 1);  //tamanho do bloco
    int blocksX = numRows/ blockWidth + 1;//qtd de threads
    int blocksY = numCols/ blockWidth + 1;
  const dim3 gridSize( blocksX, blocksY, 1);  //Tamanho do grid
  rgba_to_greyscale<<<gridSize, blockSize>>>(d_rgbaImage, d_greyImage, numRows, numCols);
  
  cudaDeviceSynchronize(); checkCudaErrors(cudaGetLastError());
}