python image compression/format conversion

foreword

Last night, I finally changed the red background to a blue one. I was thinking of submitting it happily, but
I found that 201KB could not be submitted... The college requires (60KB~200KB).

Compress image

# 代码参考自 https://blog.csdn.net/weixin_34910922/article/details/117537384
import cv2


def compress_pic(origin_img_fp, save_img_fp, compression):

    # IMWRITE_JPEG_QUALITY会比IMWRITE_PNG_COMPRESSION压缩比率低一些
    quality = cv2.IMWRITE_JPEG_QUALITY
    assert 0 <= compression <= 100, 'please make sure 0 <= compression <= 100'
    if origin_img_fp.split('.')[-1] == 'png':
        # 越小照片越大
        quality = cv2.IMWRITE_PNG_COMPRESSION
        assert 0 <= compression <= 10, 'please make sure 0 <= compression <= 10'
    
    img = cv2.imread(origin_img_fp)
    cv2.imwrite(save_img_fp.format(compression), img, [quality, compression])
    print('压缩成功', save_img_fp.format(compression))


if __name__ == '__main__':
    origin_img_path = 'pic/my_640_480.png'
    save_img_path = 'pic/my_640_480_compression_{}.png'
    compress_pic(origin_img_path, save_img_path, 8)

In png format, it can be found that the smaller the compression parameter is set, the larger the image size is.

Image format conversion

I went up and took a look, the college requires jpg format, which is really pure and pure...
I used paint to save it as a jpg image, but the result was too small, only 35KB, let 's
use python to write a png to jpg.
The quality default is 75, but the compression ratio is too large. So I turned the quality up a bit.

from PIL import Image


im = Image.open('pic/my_640_480.png')
im = im.convert('RGB')
im.save('pic/my_640_480.jpg', quality=100)

Finally finished transferring 86KB.