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equations 5 and 6

where Gx and Gy are the values of the partial derivatives along the x and y directions, respectively, at the pixel located at (i, j)of the image A.

Gx and Gy

A variety of different discrete differentiation operators exist to approximate the gradient of the image. The operator we choose in our implementation is the Sobel operator.

Gx and Gy

Like our Gaussian kernel, the Sobel operator (in both the x and y directions) is separable:

Gx and Gy Separable

Thus, we perform two separable convolutions with the separated Sobel filter on the Gaussian-filtered image to obtaingradients in the horizontal and vertical directions, and determine the magnitude and angle matrices G and Theta fromequations (5) and (6).

Non-maximum suppression and selective thresholding

Given the gradient magnitude and direction of the Gaussianfiltered image, the final step of the edge detection algorithm isto determine which pixels should be selected as edge pixels, and which should be rejected. We define two procedures, nonmaximumsuppression and selective thresholding, to gain a reasonably accurate edge map from the gradient.Non-maximum suppression selects and rejects edge pixels according to the following criteria:

  1. Pixels whose gradient magnitude is below a userdefined low threshold, tl, is immediately rejected
  2. If the gradient magnitude of a pixel is greater than that of the pixels in either direction of the gradient angleof that pixel, then the pixel is accepted if its gradient magnitude is greater than a user-defined high threshold,th

The selective thresholding technique extends on the procedure of non-maximum suppression. For any pixel that passes crtiteria(2) (maximized, relative to the neighboring pixels, along the gradient direction), consider an a x a box around the pixel.If any pixel within the box exceeds the low threshold tl, then the pixel is accepted. This technique attempts to catch pixelsthat might “connect” ridge pixels identified by criteria (2) but fail to satify the criterion themselves, in order to create morecontinuous edge lines.

Fig. 9. original image input to sobel filter

Input to Sobel filter

Fig. 10. sobel filter in both x and y applied to blurred image

figure 9 Sobel filtered in x and y directions

Fig. 11. gradient of figure 10 as 3d mesh

Gradient of Figure 10 as 3D mesh

Fig. 12. output of edge detection algorithm after non-maximum suppression and selective thresholding on the image of figure 9, with parameters tl = 70 and th = 80

Output of edge detection algorithm after non-maximum suppression and selective thresholding on the image of Figure 9, with parameters tl = 70 and th = 80

Gpu parallelization and cuda implementation

We begin with a parallelized implementation of separable convolution, since the same convolution operation is applied for both the initial Gaussian low pass filter and the edge detectingSobel filter. Our parallel implementation involves first independently computing the convolution with the horizontalfilter (h2 in Equation (2)), then convolving that result with the vertical filter h1. In computing the output y[m; n]at every index (i, j), we launch a kernel with 16 threads per block,where the total number of blocks along one dimension is equal to the size of that dimension divided by 16. For our5312 x 2988 test images, this corresponds to 332 blocks in the horizontal direction and 186 blocks in the vertical direction,each with 16 computational threads.

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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