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 ...
- 20.5k
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 ...
- 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 ...
- 919
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 ...
- 3,595
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 ...
- 26k
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 ...
- 531
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 ...
- 919
1
vote
Intensity uncertainties in 2D image
There is a concept called ergodicity. If a signal were ergodic you could use one realization of signal to estimate some of its statistical properties otherwise you have to obtain multiple realization ...
- 1,417
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 ...
- 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 ...
- 20.5k
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 ...
- 20.5k
1
vote
Estimate Local Noise Intensity in an Image
RGB cameras noise model is usually composed by:
Shot Noise.
A/D Noise (Both per pixels and correlation between columns).
Noise by the Demosaicing algorithm (Usually "colors" the noise).
...
- 20.5k
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 ...
- 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 ...
- 20.5k
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 ...
- 20.5k
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 ...
- 20.5k
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