Image processing Flashcards
What is a digital image
Discrete, sampled and quantified representation of a continues visual signal.
What can pixel transforms be used for
Changing brightness/ contrast
Name a non-linear filter and its uses
Median filter often used to remove salt/pepper noise.
What does the convolution theorem state?
The Fourier transform of a convolution is the same as the product of their Fourier transforms.
Name some edge detector filters/methods
Sobel, LoG, DoG, canny
What applications do image pyramides have?
Template matching Detection of stable points of interest Image registration Image blending Compression ...
How is the Laplace pyramid created
- Create the Gaussian pyramid
- For each layer, rescale the next layer from the gaussian pyramid
- Subtract the images and store the result in the Laplace pyramid
What is the formula for collapsing a Laplace pyramid with
3 levels
Rescale(Rescale(L3) + L2) + L1
How can we approximate the LoG filter
With a DoG filter
Name two highpass filters
LoG, DoG, Sobel, prewitt
Name two lowpass filters
Average, Gaussian Filter
What is a morphological opening?
An erosion followed by a dilation.
What morphological operations exist?
- Dilation
- Erosion
- Opening
- Closing
What is aliasing and how do you avoid it?
Sampling at lower rate than two times the highest frequency in the image. Lowpass filter to remove higher frequencies.
Mention some interpolation techniques
- Nearest neighbour
- Bilinear interpolation
- Cubic interpolation
