OpenCV压缩保存图像

imwrite

1.JPG格式图片是自带压缩的

IMWRITE_JPEG_QUALITY

For JPEG, it can be a quality from 0 to 100 (the higher is the better). Default value is 95.

IMWRITE_JPEG_PROGRESSIVE  Python: cv.IMWRITE_JPEG_PROGRESSIVE	Enable JPEG features, 0 or 1, default is False.
IMWRITE_JPEG_OPTIMIZE  Python: cv.IMWRITE_JPEG_OPTIMIZE	Enable JPEG features, 0 or 1, default is False.
IMWRITE_JPEG_RST_INTERVAL  Python: cv.IMWRITE_JPEG_RST_INTERVAL	JPEG restart interval, 0 - 65535, default is 0 - no restart.
IMWRITE_JPEG_LUMA_QUALITY  Python: cv.IMWRITE_JPEG_LUMA_QUALITY	Separate luma quality level, 0 - 100, default is -1 - don't use.
IMWRITE_JPEG_CHROMA_QUALITY  Python: cv.IMWRITE_JPEG_CHROMA_QUALITY	Separate chroma quality level, 0 - 100, default is -1 - don't use.
IMWRITE_JPEG_SAMPLING_FACTOR  Python: cv.IMWRITE_JPEG_SAMPLING_FACTOR	For JPEG, set sampling factor. See cv::ImwriteJPEGSamplingFactorParams.

2.bmp格式图片是不带任何压缩

3.PNG格式保存图像的质量是最接近原本质量的，但保存写入的速度是最慢的。

IMWRITE_PNG_COMPRESSION	For PNG, it can be the compression level from 0 to 9. A higher value means a smaller size and longer compression time. If specified, strategy is changed to IMWRITE_PNG_STRATEGY_DEFAULT (Z_DEFAULT_STRATEGY). Default value is 1 (best speed setting).
IMWRITE_PNG_STRATEGY	One of cv::ImwritePNGFlags, default is IMWRITE_PNG_STRATEGY_RLE.
IMWRITE_PNG_BILEVEL	Binary level PNG, 0 or 1, default is 0.

	double t1 = (double)getTickCount();
	double t2 = 0;	
	std::vector params;
	params.push_back(cv::IMWRITE_JPEG_QUALITY);
	params.push_back(10);
    //params.push_back(50);
    //params.push_back(100);
	cv::imwrite("C:\\test.jpg", image, params);
	t2 = ((double)getTickCount() - t1) / getTickFrequency();
	cout << "time:" << t2 << endl;

测试结果：

原图大小39.1 MB
quality 10:保存图像大小228K
quality 50:保存图像大小342K
quality 100:保存图像大小6.65M