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Image Processing
Color and pixel
colour
The three primary colors of art are red, yellow and blue; the three primary colors of color and light are red, green and blue, so a color is usually expressed as an RGB value or RGBA value (A represents the Alpha channel, which determines the pixels passing through the image, which is the transparency).
| name | RGBA value | name | RGBA value |
|---|---|---|---|
| White | (255, 255, 255, 255) | Red | (255, 0, 0, 255) |
| Green | (0, 255, 0, 255) | Blue | (0, 0, 255, 255) |
| Gray | (128, 128, 128, 255) | Yellow | (255, 255, 0, 255) |
| Black | (0, 0, 0, 255) | Purple | (128, 0, 128, 255) |
Pixel
For an image represented by a sequence of numbers, the smallest unit is the small squares of a single color on the image. These small squares have clear positions and assigned color values, and the color and position of these small squares determine They are an indivisible unit, that is, pixels (pixels). Every image contains a certain amount of pixels, which determine the size of the image on the screen.
Process images with Pillow
Crop image
from PIL import Image
image = Image.open('algorithm.jpg')
rect = 80,20,310,360
image.crop(rect).show()
Generate thumbnail
from PIL import Image
image = Image.open('algorithm.jpg')
size=128,128
image.thumbnail(size)
image.show()
Scale and paste images
from PIL import Image
image1 = Image.open('algorithm.jpg')
image2 = Image.open('road.jpg')
rect=80,20,310,360
image2_head=image2.crop(rect)
width,height=image2.size
image1.paste(image2_head.resize((int(width/1.5),int(height/1.5))),(172,40))
image1.show()
Rotate and flip
from PIL import Image
image = Image.open('algorithm.jpg')
image.rotate(180).show()
image.transpose(Image.FLIP_LEFT_RIGHT).show()
Operating pixels
from PIL import Image
image = Image.open('algorithm.jpg')
for x in range(80,310):
for y in range(20,360):
image.putpixel((x,y),(128,128,128))
image.show()
Filter effect
from PIL import Image,ImageFilter
image = Image.open('algorithm.jpg')
image.filter(ImageFilter.CONTOUR).show()