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3 votes
Accepted

Detect Longest Vertical Lines (Edges) in an Image

You may use the Dynamic Programming approach as utilized in Seam Carving for Content Aware Image Resizing. Just replace their weights with yours. Julia Implementation I implemented the idea of looking ...
Royi's user avatar
  • 19.7k
3 votes

Gaussian pyramid: why needs the image to be downsampled

In the context of a gaussian pyramid, why is the image downsampled separately although the numbers of pixels are decreased through smoothing already? The Gaussian filter adjusts the bandwidth of the ...
A_A's user avatar
  • 10.7k
2 votes

Computationally Efficient Ways of Determining If Pixels Are Clumped

Erode the image using a structuring element which is the size/shape of the maximum allowable "bad region". Then dilate using the same structuring element. This will remove the bad-but-good-enough ...
AnonSubmitter85's user avatar
2 votes

Computationally Efficient Ways of Determining If Pixels Are Clumped

Median filter? Use it to «thin out» bad pixels that appear locally sparse (for some definition of «local»). Then count the remaining bad pixels. Or convolve with a large-ish 2d kernel (eg flat ...
Knut Inge's user avatar
  • 3,434
2 votes

Computationally Efficient Ways of Determining If Pixels Are Clumped

I've not tried this, but I'm wondering if something like a simple low pass filtering, followed by a column sum will do. No time to explain code right now, but this seems to do something like what you ...
Peter K.'s user avatar
  • 25.8k
2 votes
Accepted

Converting cutoff_frequency_ratio to Cycles/Pixel in Butterworth Filtering with skimage

How can I convert cutoff_frequency_ratio to "cycles per pixel"? They are the same thing. By expressing the cut off in terms of the ratio, the physical units, whether they were samples per ...
AnonSubmitter85's user avatar
2 votes

Measuring sharpness/contrast for autofocus

Just run the image through an edge or corner filter and then take the maximum value over the entire image. This gives you the sharpness of the sharpest edge. Then refocus the camera and repeat. Since ...
Rainer P.'s user avatar
  • 531
1 vote

Slicing an Image into Tiles According to Content

Thanks to user Ash for giving me a key insight: Measuring the HSL (hue, saturation, and lightness) of the pixels can help detect where the gaps are. If I take one horizontal row of pixels that goes ...
bjnord's user avatar
  • 161
1 vote

Computationally Efficient Ways of Determining If Pixels Are Clumped

The approach I took was using MATLAB's functions, either regionprops() or bwconncomp() and ...
Royi's user avatar
  • 19.7k
1 vote

Primitive Feature Detection to Detect a Black Circle within an Image

I think you can use a much simpler method. The steps I did are: I filtered the image with an Edge Preserving Filter. I looked the profile of values along the 2 diagonals of the image. I think once ...
Royi's user avatar
  • 19.7k
1 vote
Accepted

Gaussian pyramid: why needs the image to be downsampled

In the context of a Gaussian pyramid, why is the image down-sampled separately although the numbers of pixels are decreased through smoothing already? After filtering the image the number of pixels ...
MimSaad's user avatar
  • 1,976
1 vote
Accepted

How Can PCA Be Used in Image Analysis

Imagine you have a set of 10,000 images (32 x 32) of faces. An intuitive way is to think they have a lot in common. One step farther would be that if you take one of the faces you could generate it ...
Royi's user avatar
  • 19.7k
1 vote
Accepted

Find the Mid Point of a Worm / Chain Like Object

This is a nice question. The trick to solve it, in the path I took, is creating a skeleton from the chain. This is the algorithm I came up with: Create the Skeleton I used MATLAB's ...
Royi's user avatar
  • 19.7k
1 vote

Sharpness in DCT domain image

There is no recipe for such thing. Moreover, image sharpness is not something well defined. For instance, homogenous image, is it sharp? Yet, for what we call real world images we usually have a ...
Royi's user avatar
  • 19.7k

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