data type conversion - Cuda issue on converting image to grayscale -


i having issue following code. following code takes input image , should save grayscale of it. unfortunately, seems perform expected behavior processing part of image , not whole. seems problems occurs in cudamemcpy device host.

i believe got issue while allocating memory in cuda. 

__global__ void rgb2graycudakernel(unsigned char *inputimage, unsigned char *grayimage, const int width, const int height)  {       int ty = (blockidx.x * blockdim.x) + threadidx.x;     //int tx = (blockidx.x * blockdim.x) + threadidx.x;     int tx = (blockidx.y * blockdim.y) + threadidx.y;      if( (ty < height && tx<width) )      {              float graypix = 0.0f;             float r = static_cast< float >(inputimage[(ty * width) + tx]);                       float g = static_cast< float >(inputimage[(width * height) + (ty * width) + tx]);             float b = static_cast< float >(inputimage[(2 * width * height) + (ty * width) + tx]);              graypix = (0.3f * r) + (0.59f * g) + (0.11f * b);               grayimage[(ty * width) + tx] = static_cast< unsigned char >(graypix);         }    }  //***************************************rgb2gray function, call of kernel in here ************************************* void rgb2graycuda(unsigned char *inputimage, unsigned char *grayimage, const int width, const int height) {     unsigned char *inputimage_c, *grayimage_c;     const int sizee= (width*height);      // **********memory allocation pointers , cuda******************       cudamalloc((void **) &inputimage_c, sizee);     checkcudaerror("im not alloc!");     cudamalloc((void **) &grayimage_c, sizee);     checkcudaerror("gray not alloc !");  //***********copy device*************************     cudamemcpy(inputimage_c, inputimage, sizee*sizeof(unsigned char), cudamemcpyhosttodevice);     checkcudaerror("im not send !");     cudamemcpy(grayimage_c, grayimage, sizee*sizeof(unsigned char), cudamemcpyhosttodevice);     checkcudaerror("gray not send !");     dim3 thrb(32,32);     dim3 numb (ceil(width*height/1024)); //**************execute kernel (timer in here)**************************     nstimer kerneltime = nstimer("kerneltime", false, false);     kerneltime.start();      rgb2graycudakernel<<<numb,1024>>> (inputimage_c, grayimage_c, width, height);     checkcudaerror("kernel!");     kerneltime.stop(); //**************copy host*************************     printf("/c");     cudamemcpy(grayimage, grayimage_c, sizee*sizeof(unsigned char), cudamemcpydevicetohost);     checkcudaerror("receiving data cpu failed!");  //*********************free memory***************************     cudafree(inputimage_c);     cudafree(grayimage_c);   //**********************print time****************   cout << fixed << setprecision(6); cout << "rgb2gray (cpu): \t\t" << kerneltime.getelapsed() << " seconds." << endl;  } 

const int sizee= (width*height);

should be:

const int sizee= (width*height*3);

for rgb data (1 byte per channel).

i believe in bitmap images, colors should interleaved in: 

rgb of pixel1, rgb of pixel 2 ... rgb of pixel width*height

therefore kernel should be:

__global__ void rgb2graycudakernel(unsigned char *inputimage, unsigned char *grayimage, const int width, const int height)  {       int tx = (blockidx.y * blockdim.y) + threadidx.y;     int ty = (blockidx.x * blockdim.x) + threadidx.x;      if( (ty < height && tx<width) )      {             unsigned int pixel = ty*width+tx;             float graypix = 0.0f;             float r = static_cast< float >(inputimage[pixel*3]);                       float g = static_cast< float >(inputimage[pixel*3+1]);             float b = static_cast< float >(inputimage[pixel*3+2]);              graypix = (0.3f * r) + (0.59f * g) + (0.11f * b);               grayimage[pixel] = static_cast< unsigned char >(graypix);         }    }

also, saw luminosity calculated 0.21 r + 0.72 g + 0.07 b.


Comments

Post a Comment

Popular posts from this blog

Email notification in google apps script -

https://support.google.com/docs/answer/91588?hl=en i have sheet the cells filled in data pulled via apps script, website. pull in exact same data, not. on old sheets version use able emails when data "changes" different value. new sheets, email when new data pasted cells, though exact same data......and, can't set @ ranges anymore, entire document. there easy way watch cells when data changes, , email myself? this looks lot you're trying do. for checking whether value has changed after edit, this gives necessary information it. hence, know whether new value same 1 or not. implementing "workaround" talked in second link, able compare , send email myself if value changed. initiate onedit trigger goes off onedit function uses these lines after checks in place have passed. var email = "xyz@whatever.com"; mailapp.sendemail(email, "triggermail", "a change has occurred in sheet"); note: sends "notification...
Read more

c++ - Difference between pre and post decrement in recursive function argument -

i have following sample code used pre-decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(--c); cout << c << endl; return; } } this function give output input 4 : dp3 dp2 dp1 dp0 0 1 2 3 but when use post decrement void function(int c) { if(c == 0) { return; } else { cout << "dp" << c << endl; function(c--); cout << c << endl; return; } } output goes in infinite loop dp4 can explain me in detail why happens ? this happens because function(c--) called same value of c , when finishes c decremented. recursively called, hence called same value no chance of return , hit stack overflow error. assume this, int x = 1, y = 0; y = x++ result y == 1 , x == 2. if y = ++x , bot x , y 2.
Read more

javascript - IE11 incompatibility with jQuery's 'readonly'? -

the code i'm running has no issues in firefox, or chrome. user typing 1 textbox, tabs next , can continue typing that. when run webpage on ie11, user tabs next textbox , can't type in. textbox has double-clicked before user can insert anything. i've googled , seems ie give problems when using older jquery (i.e. prefers 'prop' 'attr' ). in code below jquery's readonly keyword being used in way ie11 no longer recognise/accept? i assume issue readonly , removeclass('ignore') working expected. //when focus on textbox 1 $("#field1").focus(function() { //remove readonly property textbox 1 $('#field1').prop('readonly', false).removeclass('ignore'); //add readonly property other textboxes $('#field2, #field3, #field4') .prop('readonly', 'readonly').addclass('ignore').val(''); }); i'm using jquery 2.1.3 ...
Read more