Openni opencv kinect Bad Memory allocation - opencv

Question

Basically I've got a loop which goes through all the kinects depth pixels. If they are greater than 3000mm it sets the pixel value to black.
For some reason this works only at a close range while pointed to a wall. If I pull the kinect back (giving it a larger area to scan) I get a Bad Memory allocation error. My code can be found below. I get the bad memory allocation error inside that try catch statement. Most of the code is from the opencv kinect sample here and here.
i figured out the problem, its because the depth values are stored in an array instead of matrix, i need a better way of finding out which location in the array, the x.y of the pixels which start from 1,1 point to instead of the (i = x+y*640)
#include <opencv.hpp>
#include <iostream>
#include <string>
#include <stdio.h>
#include <OpenNI.h>
using namespace std;
using namespace cv;
int main()
{
openni::Device device;
openni::VideoStream depth;
const char* device_uri = openni::ANY_DEVICE;
openni::Status ret = openni::OpenNI::initialize();
// Open
ret =device.open( device_uri );
ret = depth.create( device, openni::SENSOR_DEPTH );
if ( ret == openni::STATUS_OK )
{
// Start Depth
depth.start();
}
// Get Depth Stream Min-Max Value
int minDepthValue = depth.getMinPixelValue();
int maxDepthValue = depth.getMaxPixelValue();
//cout << "Depth min-Max Value : " << minDepthValue << "-" << maxDepthValue << endl;
// Frame Information Reference
openni::VideoFrameRef depthFrame;
// Get Sensor Resolution Information
int dImgWidth = depth.getVideoMode().getResolutionX();
int dImgHeight = depth.getVideoMode().getResolutionY();
// Depth Image Matrix
cv::Mat dImg = cv::Mat( dImgHeight, dImgWidth, CV_8UC3 );
Mat grey= cvCreateImage(cvSize(640, 480), 8, 1); ;
for(;;)
{
depth.readFrame( &depthFrame );
openni::DepthPixel* depthImgRaw = (openni::DepthPixel*)depthFrame.getData();
for ( int i = 0 ; i < ( depthFrame.getDataSize() / sizeof( openni::DepthPixel ) ) ; i++ )
{
int idx = i * 3; // Grayscale
unsigned char* data = &dImg.data[idx];
int gray_scale = ( ( depthImgRaw[i] * 255 ) / ( maxDepthValue - minDepthValue ) );
data[0] = (unsigned char)~gray_scale;
data[1] = (unsigned char)~gray_scale;
data[2] = (unsigned char)~gray_scale;
}
openni::DepthPixel* depthpixels = (openni::DepthPixel*)depthFrame.getData();
cvtColor(dImg, grey, CV_RGB2GRAY);
int i ;
try{
for( int y =0; y < 480 ; y++){
//getting in to each pixel in a row
for(int x = 0; x < 640; x++){
//getting out the corresponding pixel value from the array
i = x+y*640;
if (depthpixels[i] >3000)
{
grey.at<unsigned char>(x,y) = 0;
}
}
}
}catch(exception e)
{cout << e.what() <<endl ;
cout <<depthpixels[i] <<endl ;
cout << i <<endl ;
}
// cv:imshow( "depth", dImg );
imshow("dpeth2", grey);
int k = cvWaitKey( 30 ); // About 30fps
if ( k == 0x1b )
break;
}
// Destroy Streams
depth.destroy();
// Close Device
device.close();
// Shutdown OpenNI
openni::OpenNI::shutdown();
return 0;
}

Answer 1

solved the problem simply by swapping my x and y around
for( y =0; y < 480 ; y++)
{
//getting in to each pixel in a row
for( x = 0; x < 640; x++)
{
if (depthpixels[i]>1500)
{
grey.at<unsigned char >(y,x) = 0;
}
if (depthpixels[i] <500)
{
grey.at<unsigned char >(y,x) = 0;
}
i++;
}
}