VLIB中边缘检测算法学习

今天以这个为例子Canny Edge Detection，来学习一下VLIB中函数在DVRRDK中的使用例子。 

Canny检测简介：相对于许多其它的边缘检测方法，比如sobel和Robert十字，Canny边缘检测器一般被认为是的首选de ,因为即使在含有噪声的图像中也能有较好的效果。

canny方法：

高斯图像平滑
2D梯度过滤
非最大抑制
滞后阈值
双阈值
边松弛

提供的API：

VLIB_Canny_Edge_Detection - 一个包装函数可以可以调用下面的所有函数。
VLIB_conv_7x7_i8_c8s - 高斯图像平滑
VLIB_xyGradientsAndMagnitude - 二维梯度过滤
VLIB_non最大抑制康力 - 非最大抑制
VLIB_doublethresholding - 双阈值
VLIB_edgeRelaxation - 边松弛

VLIB_Canny_Edge_Detection

Detailed Description

Functions
void	VLIB_Canny_Edge_Detection (const uint8_t *pInput, int16_t *pBufGradX, int16_t *pBufGradY, int16_t *pBufMag, uint8_t *pBufOut, uint8_t *pScratch, int32_t *numItems, uint16_t width, uint16_t height)
void	VLIB_conv_7x7_i8_c8s (const uint8_t *restrict imgin_ptr, uint8_t *restrict imgout_ptr, uint32_t width, int16_t pitch, const int8_t *restrict mask_ptr, int16_t shift)
int32_t	VLIB_nonMaximumSuppressionCanny (const int16_t *restrict pInMag, const int16_t *restrict pInGradX, const int16_t *restrict pInGradY, uint8_t *restrict pOut, uint16_t width, uint16_t pitch, uint16_t height)
int32_t	VLIB_doublethresholding (const int16_t *restrict pInMag, uint8_t *edgeMap, uint32_t *restrict strongEdgeListPtr, int32_t *numStrongEdges, uint16_t width, uint16_t pitch, uint16_t height, uint8_t loThresh, uint8_t hiThresh, uint32_t pos_frm)
int32_t	VLIB_edgeRelaxation (uint8_t *edgeMap, uint32_t *restrict strongEdgeListPtr, const int32_t *numStrongEdges, uint16_t width) Function Documentation void VLIB_Canny_Edge_Detection ( const uint8_t *  pInput,     int16_t *  pBufGradX,     int16_t *  pBufGradY,     int16_t *  pBufMag,     uint8_t *  pBufOut,     uint8_t *  pScratch,     int32_t *  numItems,     uint16_t  width,     uint16_t  height     )   Description: This function is a wrapper function around the full Canny Edge Detection algorithms. It internally calls, in sequence on the image: VLIB_conv_7x7_i8_c8s (image smoothing), VLIB_xyGradientsAndMagnitude, VLIB_nonMaximumSuppressionCanny, VLIB_doublethresholding and VLIB_edgeRelaxation. It requires externally allocated intermediate buffers to be provided and takes care of border conditions in between internal function calls. The above mentioned APIs are independently callable in case a different sequence is required, intermeidate processing is required, or differ buffer management is required. Parameters: [in]  *pInput  Pointer to input image array [out]  *pBufGradX  Pointer to array containing X gradient [out]  *pBufGradY  Pointer to array containing Y gradient [out]  *pBufMag  Pointer to array containing magnitude [out]  *pBufOut  Pointer to output buffer [out]  *pScratch  Pointer to scratch buffer [out]  *numItems  Pointer to scalar number of items [in]  width  Input width [in]  height  Input height Assumptions: The input array and output arrays should not overlap The output array must be 32-bit aligned The width parameter must be a multiple of 2 and >= 18 The height parameter must be > 10 pBufGradX should be a buffer of (width * height * 2) bytes pBufGradY should be a buffer of (width * height * 2) bytes pBufMag should be a buffer of (width * height * 2) bytes pBufOut should be a buffer of (width * height) bytes pScratch should be a buffer of (width * height) bytes