For the feature of the liver B-ultrasound image, we adopt the Gaussian low-pass filter and contrast-stretching transformation methods.

针对肝脏B超声图像的特点，本文在对图像进行预处理时采用了高斯低通滤波与灰度拉伸相结合的技术。

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When the image (host information) is added a noise, gaussian low-pass filter, shear attacks, the mandible, extract the original watermark image watermark image and the similarity is very satisfactory;

当图像（宿主信息）遭到加噪、高斯低通滤波、剪切等攻击后，其可视度、提取的水印图像与原始水印图像的类似度都是十分令人称心的；

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According to the need of precision, 5 cascaded low pass filter approaching the analog Gaussian low pass filter.

根据精度要求，模拟高斯低通滤波器采用5阶低通滤波器来进行逼近。

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