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atan on GPU

asked 2015-08-11 06:00:31 -0500

Durden gravatar image

Hello,

I am developing a function that does per-pixel operations on an image and there is a step where I have to compute the arctan (atan) for each pixel. I have not found any atan function for GPU that I can embed in my code. I pasted my code below.

Is there anyone that can help me with this problem? I would like to perform atan on GPU because I have other operations to do (e.g. pixels normalization etc.) afterwards.

Thank you in advace,

Durden

cv::Mat host_img = cv::imread("/home/ubuntu/myCodes/firstTest/img/frame.png");

// CPU declarations
cv::Mat b(host_img.size(), CV_8UC1);
cv::Mat g(host_img.size(), CV_8UC1);
cv::Mat r(host_img.size(), CV_8UC1);

cv::Mat b_norm(host_img.size(), CV_64FC1);
cv::Mat g_norm(host_img.size(), CV_64FC1);
cv::Mat r_norm(host_img.size(), CV_64FC1);

vector<cv::Mat> final_img;
cv::Mat out_img(host_img.size(), CV_8UC3);

// GPU declarations
cv::gpu::GpuMat img_gpu(host_img.size(), CV_8UC3);

cv::gpu::GpuMat b_gpu(host_img.size(), CV_8UC1);
cv::gpu::GpuMat g_gpu(host_img.size(), CV_8UC1);
cv::gpu::GpuMat r_gpu(host_img.size(), CV_8UC1);

vector<cv::gpu::GpuMat> chans_gpu(3);
chans_gpu[0].create(host_img.rows, host_img.cols, CV_8UC1);
chans_gpu[1].create(host_img.rows, host_img.cols, CV_8UC1);
chans_gpu[2].create(host_img.rows, host_img.cols, CV_8UC1);

img_gpu.upload(host_img);
cv::gpu::split(img_gpu, chans_gpu);

cv::gpu::max(chans_gpu[1], chans_gpu[2], b_gpu);
cv::gpu::max(chans_gpu[0], chans_gpu[2], g_gpu);
cv::gpu::max(chans_gpu[0], chans_gpu[1], r_gpu);

chans_gpu[0].convertTo(chans_gpu[0], CV_64FC1);
chans_gpu[1].convertTo(chans_gpu[1], CV_64FC1);
chans_gpu[2].convertTo(chans_gpu[2], CV_64FC1);

b_gpu.convertTo(b_gpu, CV_64FC1);
g_gpu.convertTo(g_gpu, CV_64FC1);
r_gpu.convertTo(r_gpu, CV_64FC1);

cv::gpu::divide(chans_gpu[0], b_gpu, b_gpu);
cv::gpu::divide(chans_gpu[1], g_gpu, g_gpu);
cv::gpu::divide(chans_gpu[2], r_gpu, r_gpu);

b_gpu.download(b);
g_gpu.download(g);
r_gpu.download(r);

for (int i=0 ; i<b.rows ; i++) {
    for (int j=0 ; j<b.cols ; j++) {
        b_norm.at<double>(i,j) = atan(b.at<double>(i,j));
        g_norm.at<double>(i,j) = atan(g.at<double>(i,j));
        r_norm.at<double>(i,j) = atan(r.at<double>(i,j));
    }
}
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answered 2015-08-11 09:59:30 -0500

Guyygarty gravatar image

CUDA has an Atan function but I don't know if it is accessible through OpenCV or you would need to write your own kernel to use it.

Another way would be to implement the Euler series (the Taylor series converges too slowly to be of much use):

image description

using per element multiplication, division and summations.

guy

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there is something here too

LBerger gravatar imageLBerger ( 2015-08-11 10:01:32 -0500 )edit

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Asked: 2015-08-11 06:00:31 -0500

Seen: 476 times

Last updated: Aug 11 '15