tailieunhanh - Lecture Digital image processing - Lecture 12: Image enhancement

After studying this chapter you will be able to understand: Necessity of image enhancement, image enhancement techniques broad categories, one of the category is spatial domain operations In spatial domain operations, frequency domain operations. | Digital Image Processing CSC331 Image Enhancement 1 Summery of previous lecture Analyze the computational complexity of image transform operations The separable transformation computational complexity reduction of the separable transformation 2 Todays lecture Necessity of image enhancement. Image enhancement techniques broad categories. One of the category is spatial domain operations In spatial domain operations, point processing, histogram based processing techniques mask processing techniques Frequency domain operations 3 4 What is image enhancement? 5 Types of image enhancement techniques 6 7 Neighborhood of the point (x, y) point processing the transformation operator T operates at point (x, y) considering a certain neighborhood of the point (x, y) neighborhood size of 3 by 3 around point (x, y). Different applications, the neighborhood size may be different . neighborhood size of 5 by 5, 7 by 7 8 single pixel location 9 Point processing plotting 10 1x1 is also Threshold operation Mask operation 11 W I,j are also called coefficients coefficient values Different point processing techniques are used according to its need The coefficient values different (W values) in the mask determine the kind of image enhancement operations image sharpening operation image averaging operation s enhancement operations All of them depend upon the mask values that is the w ij present in this particular mask. 12 Negative image 13 Result of Negative image 14 Contrast enhancement Dark images Various reasons The object or scene illumination is poor Dynamic range can not be capture by the sensor The aperture of the lens of the camera not properly set 15 Low Contrast image 16 Transformation for contrast operation 17 Result of contrast enhancement 18 Dynamic range enhancement We need to reduce the dynamic range An image with high dynamic range cannot be properly reproduced by some display device. If a gray level display device uses bits to display intensity levels from 0 to 255 | Digital Image Processing CSC331 Image Enhancement 1 Summery of previous lecture Analyze the computational complexity of image transform operations The separable transformation computational complexity reduction of the separable transformation 2 Todays lecture Necessity of image enhancement. Image enhancement techniques broad categories. One of the category is spatial domain operations In spatial domain operations, point processing, histogram based processing techniques mask processing techniques Frequency domain operations 3 4 What is image enhancement? 5 Types of image enhancement techniques 6 7 Neighborhood of the point (x, y) point processing the transformation operator T operates at point (x, y) considering a certain neighborhood of the point (x, y) neighborhood size of 3 by 3 around point (x, y). Different applications, the neighborhood size may be different . neighborhood size of 5 by 5, 7 by 7 8 single pixel location 9 Point processing plotting 10 1x1 is also Threshold .