> Unify Compute Platform (UCP) > Vision Process > Vision Algorithm > Threshold Thresholding function to process the image by different thresholding methods.
This function applies a fixed level of thresholding to a multi-channel array.
It is typically used to obtain a binary image from a grayscale image or for noise removal, i.e., filtering out pixels with values that are too small or too large.
This function currently supports the HB_VP_THRESH_TOZERO type of threshold.
Operator Effect
Principle
Different threshold types have different processing effects, which are based on the following principles:
The principle expression formula is as follows:
T H R E S H B I N A R Y : d s t ( x , y ) = { m a x v a l i f s r c ( x , y ) > t h r e s h 0 o t h e r w i s e T H R E S H B I N A R Y I N V : d s t ( x , y ) = { 0 i f s r c ( x , y ) > t h r e s h m a x v a l o t h e r w i s e T H R E S H T R U N C : d s t ( x , y ) = { t h r e s h o l d i f s r c ( x , y ) > t h r e s h s r c ( x , y ) o t h e r w i s e T H R E S H T O Z E R O : d s t ( x , y ) = { s r c ( x , y ) i f s r c ( x , y ) > t h r e s h 0 o t h e r w i s e T H R E S H T O Z E R O I N V : d s t ( x , y ) = { 0 i f s r c ( x , y ) > t h r e s h s r c ( x , y ) o t h e r w i s e \begin{aligned}\begin{aligned}THRESH\quad BINARY : \quad dst(x,y)&=\begin{cases} maxval & if src(x,y)>thresh \\ 0 & otherwise \end{cases} \\THRESH\quad BINARY\quad INV : \quad dst(x,y)&=\begin{cases} 0 & if src(x,y)>thresh \\ maxval & otherwise \end{cases} \\THRESH\quad TRUNC : \quad dst(x,y)&=\begin{cases} threshold & if src(x,y)>thresh \\ src(x,y) & otherwise \end{cases} \\THRESH\quad TOZERO: \quad dst(x,y)&=\begin{cases} src(x,y) & if src(x,y)>thresh \\ 0 & otherwise \end{cases} \\THRESH\quad TOZERO\quad INV: \quad dst(x,y)&=\begin{cases} 0 & if src(x,y)>thresh \\ src(x,y) & otherwise \end{cases}\end{aligned}\end{aligned} T H R E S H B I N A R Y : d s t ( x , y ) T H R E S H B I N A R Y I N V : d s t ( x , y ) T H R E S H T R U N C : d s t ( x , y ) T H R E S H T O Z E R O : d s t ( x , y ) T H R E S H T O Z E R O I N V : d s t ( x , y ) = { ma xv a l 0 i f sr c ( x , y ) > t h r es h o t h er w i se = { 0 ma xv a l i f sr c ( x , y ) > t h r es h o t h er w i se = { t h r es h o l d sr c ( x , y ) i f sr c ( x , y ) > t h r es h o t h er w i se = { sr c ( x , y ) 0 i f sr c ( x , y ) > t h r es h o t h er w i se = { 0 sr c ( x , y ) i f sr c ( x , y ) > t h r es h o t h er w i se
API Interface
int32_t hbVPThreshold ( hbUCPTaskHandle_t * taskHandle , hbVPImage * dstImg , hbVPImage const * srcImg , hbVPThresholdParam const * thresholdParam); For detailed interface information, please refer to hbVPThreshold .
Usage
// Include the header #include "hobot/hb_ucp.h" #include "hobot/vp/hb_vp.h" #include "hobot/vp/hb_vp_threshold.h" // init Image, allocate memory for image data hbUCPSysMem src_mem; hbUCPMallocCached ( & src_mem , src_stride * src_height , 0 ); hbVPImage src_img{HB_VP_IMAGE_FORMAT_Y , HB_VP_IMAGE_TYPE_U8C1 , src_width , src_height , src_stride , src_mem . virAddr , src_mem . phyAddr , nullptr , 0 , 0 }; hbUCPSysMem dst_mem; hbUCPMallocCached ( & dst_mem , dst_stride * dst_height , 0 ); hbVPImage dst_img{HB_VP_IMAGE_FORMAT_Y , HB_VP_IMAGE_TYPE_U8C1 , dst_width , dst_height , dst_stride , dst_mem . virAddr , dst_mem . phyAddr , nullptr , 0 , 0 }; // init param hbVPThresholdParam threshold_param; threshold_param.thresh = 0 ; threshold_param.type = HB_VP_THRESH_TOZERO; // init task handle and schedule param hbUCPTaskHandle_t task_handle{nullptr}; hbUCPSchedParam sched_param; HB_UCP_INITIALIZE_SCHED_PARAM ( & sched_param); sched_param.backend = HB_UCP_DSP_CORE_0; // create task hbVPThreshold ( & task_handle , & dst_img , & src_img , & threshold_param); // submit task hbUCPSubmitTask (task_handle , & sched_param); // wait for task done hbUCPWaitTaskDone (task_handle , 0 ); // release task handle hbUCPReleaseTask (task_handle); // release memory hbUCPFree ( & src_mem); hbUCPFree ( & dst_mem); 
