TAILIEUCHUNG - Lecture Digital image processing - Lecture 16: Image enhancement

This chapter presents the following content: 1st and 2nd order derivatives, laplacian filter, unsharp masking and high-boost filtering, mask processing, linear smoothing operation, median filter, sharpening spatial filter. | Digital Image Processing CSC331 Image Enhancement 1 Summery of previous lecture Mask processing Linear smoothing operation Median filter Sharpening spatial filter 2 Todays lecture 1st and 2nd order derivatives Laplacian filter Unsharp masking and high-boost filtering 3 Smoothing linear filters with different mask size 4 5 Salt-and-pepper noise 6 Sharpening The term sharpening is referred to the techniques suited for enhancing the intensity transitions. In images, the borders between objects are perceived because of the intensity change: more crisp the intensity transitions, more sharp the image. The intensity transitions between adjacent pixels are related to the derivatives of the image. Hence, operators (possibly expressed as linear filters) able to compute the derivatives of a digital image are very interesting 7 Sharpening spatial filter By averaging over an image, then the image becomes blurred or the details in the image are removed. Now, this averaging operation is equivalent to integration operation. The opposite differentiation operation or derivative operations will make the image sharp. We need derivative operations 8 First derivative of an image Since the image is a discrete function, the traditional definition of derivative cannot be applied. Hence, a suitable operator have to be defined such that it satisfies the main properties of the first derivative: 1. it is equal to zero in the regions where the intensity is constant; 2. it is different from zero for an intensity transition; 3. it is constant on ramps where the intensity transition is constant. The natural derivative operator is the difference between the intensity of neighboring pixels (spatial differentiation). 9 Second derivative of an image This operator satisfies the following properties: 1. it is equal to zero where the intensity is constant; 2. it is different from zero at the begin of a step (or a ramp) of the intensity; 3. it is equal to zero on the constant slope ramps. 10 11 12 .

• Đồ họa - Thiết kế - Flash
• Digital image processing
• Lecture Digital image processing
• Digital images
• Digital computers
• Image processing
• Laplacian filter
• Image segmentation
• Local processing
• Global processing
• Morphological image processing
• Autonomous machine applications
• Region growing
• Image digitization
• Theory of sampling
• Image transformation
• Image enhancement
• Image restoration
• Image transform
• Image compression
• Dark image