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  • problem when trying to empty a stack in c

    - by frx08
    Hi all, (probably it's a stupid thing but) I have a problem with a stack implementation in C language, when I try to empty it, the function to empty the stack does an infinite loop.. the top of the stack is never null. where I commit an error? thanks bye! #include <stdio.h> #include <stdlib.h> typedef struct stack{ size_t a; struct stack *next; } stackPos; typedef stackPos *ptr; void push(ptr *top, size_t a){ ptr temp; temp = malloc(sizeof(stackPos)); temp->a = a; temp->next = *top; *top = temp; } void freeStack(ptr *top){ ptr temp = *top; while(*top!=NULL){ //the program does an infinite loop *top = temp->next; free(temp); } } int main(){ ptr top = NULL; push(&top, 4); push(&top, 8); //down here the problem freeStack(&top); return 0; }

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  • Why I get a segmentation fault?

    - by frx08
    Why I get a segmentation fault? int main() { int height, width, step, step_mono, channels; int y, x; char str[15]; uchar *data, *data_mono; CvMemStorage* storage = cvCreateMemStorage(0); CvSeq* contour = 0; CvPoint* p; CvFont font; CvCapture *capture; IplImage *frame = 0, *mono_thres = 0; capture = cvCaptureFromAVI("source.avi"); //capture video if(!cvGrabFrame(capture)) exit(0); frame = cvRetrieveFrame(capture); //capture the first frame from video source cvNamedWindow("Result", 1); while(1){ mono_thres = cvCreateImage(cvGetSize(frame), 8, 1); height = frame -> height; width = frame -> width; step = frame -> widthStep; step_mono = mono_thres -> widthStep; channels = frame -> nChannels; data = (uchar *)frame -> imageData; data_mono = (uchar *)mono_thres -> imageData; //converts the image to a binary highlighting the lightest zone for(y=0;y < height;y++) for(x=0;x < width;x++) data_mono[y*step_mono+x*1+0] = data[y*step+x*channels+0]; cvThreshold(mono_thres, mono_thres, 230, 255, CV_THRESH_BINARY); cvFindContours(mono_thres, storage, &contour, sizeof(CvContour), CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE); //gets the coordinates of the contours and draws a circle and the coordinates in that point p = CV_GET_SEQ_ELEM(CvPoint, contour, 1); cvCircle(frame, *p, 1, CV_RGB(0,0,0), 2); cvInitFont(&font, CV_FONT_HERSHEY_PLAIN, 1.1, 1.1, 0, 1); sprintf(str, "(%d ,%d)", p->x, p->y); cvPutText(frame, str, cvPoint(p->x+5,p->y-5), &font, CV_RGB(0,0,0)); cvShowImage("Result", mono_thres); //next frame if(!cvGrabFrame(capture)) break; frame = cvRetrieveFrame(capture); if((cvWaitKey(10) & 255) == 27) break; } cvReleaseCapture(&capture); cvDestroyWindow("Result"); return 0; }

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  • Draw and move a point over an image in python

    - by frx08
    Hi all I have to do a little script in Python. In this script I have a variable (that represents a coordinate) that is continuously updated to a new value. So I have to draw a red point over a image and update the point position every time the variable that contains the coordinate is updated. I tried to explain what I need doing something like this but obviously it doesn't works: import Tkinter, Image, ImageDraw, ImageTk i=0 root = Tkinter.Tk() im = Image.open("img.jpg") root.geometry("%dx%d" % (im.size[0], im.size[1])) while True: draw = ImageDraw.Draw(im) draw.ellipse((i, 0, 10, 10), fill=(255, 0, 0)) pi = ImageTk.PhotoImage(im) label = Tkinter.Label(root, image=pi) label.place(x=0, y=0, width=im.size[0], height=im.size[1]) i+=1 del draw someone may help me please? thanks very much!

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