Preliminary study on Digital image processing

The grayscale graph is a two-dimensional function, and the color graph is three two-dimensional function.

The smaller the quantization level of digital image, the worse the color.

The sampling interval is also the pixel.

The more actual levels in the image, the better the effect.

The contrast of the image = maximum brightness/minimum brightness, the greater the contrast, the better the image effect.

The processing of the histogram: The image is dark, the histogram of the image is distributed in the lower gray level, and the image is on the side of the high gray level. The pixels of a good image occupy all gray levels and are evenly distributed, with high contrast and varying shades of gray.

Image sharpening of three kinds of operators: (image sharpening is mainly used to enhance the image of gray-scale transition part)

1. Image enhancement-gradient operator based on first-order derivative

The direction of the gradient is the direction of the maximum rate of change of function f (x, y).

Original

• Robert Cross Gradient Code

I=imread (' 123.jpg ');
Imshow (I);
I=double (I);
W1=[-1 0;0 1];
W2=[0-1;1 0];
G1=imfilter (I,W1, ' Corr ', ' replicate ');
G2=imfilter (I,W1, ' Corr ', ' replicate ');
G=abs (G1) +abs (G2);
Figure,imshow (g,[]);
Figure,imshow (ABS (G1), []);
Figure,imshow (ABS (G2), []);

(Do not understand how this code is written, do not understand what the function of this operator, from the image can not see the effect)

• Sobel Gradient Code

I=imread (' 123.jpg ');
W1=fspecial (' Sobel ');
W2=w1 ';
G1=imfilter (I,W1);
G2=imfilter (I,W2);
G=abs (G1) +abs (G2);
Figure,imshow (g,[]);
Figure,imshow (g1,[]);
Figure,imshow (g2,[]);

W1 W2

(Do not understand how this code is written, do not understand what the role of this operator, from the image is to remove the effect of the background)

2. Image Enhancement-Laplace operator based on second-order differential

Application: Emphasize the mutation of gray scale in image and decrease the area of gray scale slow change

Code

I=imread (' 123.jpg ');
Figure,imshow (i,[]);
Id=double (I);
H_lap=[-1-1 -1;-1 8-1;-1-1-1]
I_lap=imfilter (Id,h_lap, ' Corr ', ' replicate ');
Figure,imshow (Uint8 (ABS (I_LAP)), []);

(Do not understand how this code is written, do not understand what the role of this operator, from the image is to remove the background, and the above effect is not the same as the background)

This makes the contents of the shoes and boots serious today, and there is no clear place to slowly supplement the study later.

Preliminary study on Digital image processing