练习1 图像处理基本绘制操作(附matlab+python代码)

题目：
1.读取灰度图
2. 灰度图：
绘制黑色方块、黑白棋盘格、白色三角块

3.彩色图：
绘制红色圆盘、白色椭圆轮廓

代码：

灰度图:

#python
import cv2
img = cv2.imread('lena_512.jpg')
gray = img[:,:,0]
blue = img[:,:,0]
green = img[:,:,1]
red = img[:,:,2]
[h,w]=img.shape[:2]
for i in range(h):
   for j in range(w):
       gray[i,j]=blue[i,j]*0.114+green[i,j]*0.587+red[i,j]*0.299
cv2.imshow('image',gray)
cv2.waitKey(0)
cv2.destroyAllWindows()

% matlab
img =imread('cat.jpg');
gray=img(:,:,1);
blue=img(:,:,1);
green=img(:,:,2);
red=img(:,:,3);
[h,w]=size(img);
for i=1:h
    
    for j=1:w/3
        gray(i,j)=blue(i,j)*0.114+green(i,j)*0.587+red(i,j)*0.299;
        
    end
end
imshow(gray)

画方块

#python
import cv2
img = cv2.imread('lena_512.jpg')
h,w = img.shape[:2]
x = h//3
y = w//3
for i in range(x,2*x):
    for j in range(y,2*y):
        img[i,j,:]=255
cv2.imshow('image',img)
cv2.waitKey(0)
cv2.destroyAllWindows()

% matlab
[a,b]=size(gray);
x=floor(a/3);
y=floor(b/3);
for i=x:2*x
    for j=y:2*y
        gray(i,j)=255;
    end
end
imshow(gray);

画红圆

#python
import cv2
img = cv2.imread('lena_512.jpg')
h,w = img.shape[:2]
x = h//3
y = w//3
for i in range(h):
    for j in range(w):
        if (pow((x-i)*(x-i)+(y-j)*(y-j),0.5)<50):
            img[i,j,0] = 0
            img[i,j,1] = 0
            img[i,j,2] = 255

cv2.imshow('image',img)
cv2.waitKey(0)
cv2.destroyAllWindows()

%matlab
img=imread('cat.jpg');
[h,w]=size(img);
x = floor(h/2);
y = floor(w/6);
for i=1:h
    for j=1:w/3
        if (x-i)*(x-i)+(y-j)*(y-j)<2500
            img(i,j,1) = 255;
            img(i,j,2) = 0;
            img(i,j,3) = 0;
        end
    end
end
imshow(img)

画三角块

画黑白棋盘格

画椭圆