CSCE4240 - Exam 2 Flashcards
histogram algorithm
step 1.
create a one-dimensional array h of size L with initial value of zero
histogram algorithm
step 1. create one-dimensional array h of size L with initial value of zero
step 2.
loop through all pixels in the image A
histogram algorithm
step 1. create one-dimensional array h of size L with initial value of zero
step 2. loop through all pixels in the image
step 3.
for a pixel value v, increase the value at h(v) by one
histogram algorithm
step 1. create one-dimensional array h of size L with initial value of zero
step 2. loop through all pixels in the image
step 3. for a pixel value v, increase the value of h(v) by one
step 4.
continue until all pixels in the image A are visited
what is an image histogram
acts as a graphical representation of the tonal distribution in a digital image
what is histogram stretching
maps the value of all pixels to a new value that spans the full gray scale range
what is histogram equalization
maximize the usage of the full brightness range. maximum contrast is achieved when image histogram is uniform distribution
median filter algorithm
sort all the pixels in an increasing order and take the middle value
what are sampling rates
rate at which amplitude values are digitized from the original waveform
what is sinusoidal basis
use smoothly-varying sinusoidal patters at different frequencies, angles for basis of images - hadamard basis doesn’t capture real image gradients
what is magnitude
how much of a certain frequency component is in an image
what is phase
where that certain frequency lies
butterworts lowpass filter
introduces unwanted artifacts into the result. uses smooth transition
JPEG encoding
step 1.
transform RGB to YUV and subsample color
JPEG encoding
step 1. transform RGB to YUV and subsample color
step 2.
perform discrete cosine transform on 8x8 image blocks
JPEG encoding
step 1. transform RGB to YUV and subsample color
step 2. perform discrete cosine transform on 8x8 image blocks
step 3.
perform quantization
JPEG encoding
step 1. transform RGB to YUV and subsample color
step 2. perform discrete cosine transform on 8x8 image blocks
step 3. perform quantization
step 4.
zig-zag ordering and run-length encoding
JPEG encoding
step 1. transform RGB to YUV and subsample color
step 2. perform discrete cosine transform on 8x8 image blocks
step 3. perform quantization
step 4. zig-zag ordering and run-length encoding
step 5.
entropy encoding
what is quantization
aims at reducing the total number of bits by dividing each entry in the frequency space block by an integer then round
wavelet-based image fusion
step 1.
decompose images using wavelet transform
wavelet-based image fusion
step 1. decompose images using wavelet transform
step 2.
combine coefficients
- combine approximation subbing and the average
- select the maximum among detail subtends and put in the composite