python cv2圖像質(zhì)量壓縮的算法示例
使用opencv對圖像進行編碼,一方面是圖像二進制傳輸?shù)男枰硪环矫鎸D像壓縮。以jpeg壓縮為例:
1、轉(zhuǎn)為二進制編碼img = cv2.imread(img_path)# 取值范圍:0~100,數(shù)值越小,壓縮比越高,圖片質(zhì)量損失越嚴重params = [cv2.IMWRITE_JPEG_QUALITY, ratio] # ratio:0~100msg = cv2.imencode('.jpg', img, params)[1]msg = (np.array(msg)).tobytes()print('msg:', len(msg))
對于png壓縮,改為:
# 取值范圍:0~9,數(shù)值越小,壓縮比越低,圖片質(zhì)量越高params = [cv2.IMWRITE_PNG_COMPRESSION, ratio] # ratio: 0~9msg = cv2.imencode('.png', img, params)[1]msg = (np.array(msg)).tobytes()
對于圖像解碼,使用imdecode即可解為numpy類型圖像:
img = cv2.imdecode(np.frombuffer(msg, np.uint8), cv2.IMREAD_COLOR)print(img.shape, type(img))2、圖像質(zhì)量壓縮
原圖(48k):
jpg壓縮:
img_path = r'E:img.jpg'img = cv2.imread(img_path)cv2.imwrite(r'E:ret_80.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 80])cv2.imwrite(r'E:ret_40.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 40])cv2.imwrite(r'E:ret_10.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 10])cv2.imwrite(r'E:ret_0.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 0])
結(jié)果:
壓縮后圖像大小依次為:49.6K、25.6K、11K、5.02K。jpg壓縮明顯,壓縮到極致時顏色信息損失嚴重。
png壓縮:
img_path = r'E:img.jpg'img = cv2.imread(img_path)cv2.imwrite(r'E:ret_0.png', img, [cv2.IMWRITE_PNG_COMPRESSION, 0])cv2.imwrite(r'E:ret_3.png', img, [cv2.IMWRITE_PNG_COMPRESSION, 3])cv2.imwrite(r'E:ret_6.png', img, [cv2.IMWRITE_PNG_COMPRESSION, 6])cv2.imwrite(r'E:ret_9.png', img, [cv2.IMWRITE_PNG_COMPRESSION, 9])
結(jié)果:
壓縮后圖像大小依次為:675K、364K、364K、360K。png格式偏大,壓縮率調(diào)到最高也還有360K,且成像上無明顯變化。
PS:也可以對圖像壓縮后保存,如:
img_path = r'E:img.jpg'img = cv2.imread(img_path)params = [cv2.IMWRITE_PNG_COMPRESSION, 0]msg = cv2.imencode('.png', img, params)[1]msg = (np.array(msg)).tobytes()print('msg:', len(msg))img = cv2.imdecode(np.frombuffer(msg, np.uint8), cv2.IMREAD_COLOR)cv2.imwrite(rr'E:ret.jpg', img)
bug處理:
早期版本這樣寫:
msg = (np.array(msg)).tostring()改為:msg = (np.array(msg)).tobytes() img = cv2.imdecode(np.fromstring(msg, np.uint8), cv2.IMREAD_COLOR)改為:img = cv2.imdecode(np.frombuffer(msg, np.uint8), cv2.IMREAD_COLOR)
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