水岸彩色图像自适应阈值边缘提取算法

水岸彩色图像边缘提取是图像基础处理的难题。阐述了所提出的方法：依据纵向灰度最大差之和与图像灰度平均值间的模糊关系确定梯度阈值;运用平均值与中值协调方式滤波,在求中值群时拓展了Paeth提出的简化求中值算法以提高运算速度;在边界提取时选取有一定间距的像素分别计算三原色梯度,把其中绝对值最大的梯度作为边界存在的判据之一,同时根据二阶导数符号变化提取边界。算法对不同时刻和不同天气状况下的大量图像进行处理,结果表明能较好地自适应调整阈值,提取出的边界受噪声等影响产生的伪边界点和边界断点少,提高了边界点的有效性和连续性。它适用于对水岸彩色图像的概括性识别前期处理。

Efficient Approach of Edge Detection of Near Bank Images

A new four steps edge detection method was proposed.First,the threshold was calculated in natura illumination according to fuzzy logic between sum of the largest differences of gray level values of column pixels and mean gray values of the image.Second,a compromise between even and median filter was introduced to filter noises of image.Meanwhile,one simple approach,which was based on paeth'method,was employed to obtain group of medians in order to decrease the operation time.Third,the gradient between two pixels that have certain distance was calculated in three color components respectively,and then the maximum of gradients of the three was attained.And if absolute value of the maximum gradients exceeds of red,green and blue a threshold that calculated in first step,a candidate for edges is said to exist.Finally,the candidate is converted to edge according to zero-crossing of second derivatives.The algorithm we proposed is applied to images in various weather conditions and times in a day to detect edges,and experimental results indicate that edges detected are continuous and effective.