c++ - how to change Width Scale in Opencv Histogram.(640 X 480) -

how change width scale in opencv histogram.

my code result express width 0 ~ 255, want change width 640 use scale. , want find mistakes on code, , suggest me solution..

please me.

void mainwindow::basic_histogram(iplimage* timage) {     iplimage* canvas;     int hist[256];     double scale=1;     int i,j,max=0;     qimage pimage;      canvas = cvcreateimage(cvsize(640, 480), ipl_depth_8u, 3);     cvset(canvas,cv_rgb(255,255,255),0);      for(i=0;i<256;i++)     {         hist[i]=0;     }      for(i=0;i<timage->height;i++)     {         for(j=0;j<timage->width;j++)         {             hist[(uchar)timage->imagedata[(i * timage->widthstep) + j]]++;         }     }      max = 256 * 10;       (i = 0; < 256; i++)     {         max = hist[i] > max ? hist[i] : max;     }        scale = max > canvas->height ? (double)canvas->height/max : 1.;       (i = 0; < 256; i++)      {          cvpoint pt1 = cvpoint(i, canvas->height - (hist[i] * scale));          cvpoint pt2 = cvpoint(i, canvas->height);          cvline(canvas, pt1, pt2, cv_rgb(0,0,0), 1, 8, 0);      }       pimage = iplimage2qimage(canvas);       emit newedgeframe(pimage);       cvreleaseimage(&canvas);  } 

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below picture show code result.