Im currently trying to deal with my hw. But i don't know how to approach this problem. For example here is a putpixel function i wrote that draws a circle:

void cember(){
  int r=50;
  const int width=r;
  const int length=r*1.5;
  for(int y=width;y>= -width;y-=2){
    for(int x=-length;x<=length;x  ){
        if ((int) hesapla(x,y)==r)
        putpixel(x 50,y 50,WHITE);
      }
      
  }
  getch();
  

}

Lets say i want to crop a square shaped piece from it with only using graphics.h library. What can i do? I couldnt even write some codes. I wrote a function that's square shaped but couldnt get any further than that.

The reason im using putpixel instead of circle function is im not allowed to. Can you help me?

CodePudding user response：

1. The circle function.

void GUI_Circle(int32_t xCentre, int32_t yCentre, int32_t radius, uint32_t colour)
{
    int32_t x = 0, y = radius;
    int32_t d = 3 - (2 * radius);

    if (colour == UINT32_MAX) return;

    while(x <= y)
    {
        //right bottom
        if((xCentre   x) >=0 && (yCentre   y) >= 0 && (xCentre   x) < ScreenXsize && (yCentre   y) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre   x, yCentre   y);
        if((xCentre   y) >=0 && (yCentre   x) >= 0 && (xCentre   y) < ScreenXsize && (yCentre   x) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre   y, yCentre   x);

        //left bottom
        if((xCentre - x) >=0 && (yCentre   y) >= 0 && (xCentre - x) < ScreenXsize && (yCentre   y) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre - x, yCentre   y);
        if((xCentre - y) >=0 && (yCentre   x) >= 0 && (xCentre - y) < ScreenXsize && (yCentre   x) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre - y, yCentre   x);

        //Top right
        if((xCentre   y) >=0 && (yCentre - x) >= 0 && (xCentre   y) < ScreenXsize && (yCentre - x) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre   y, yCentre - x);
        if((xCentre   x) >=0 && (yCentre - y) >= 0 && (xCentre   x) < ScreenXsize && (yCentre - y) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre   x, yCentre - y);

        // Top left
        if((xCentre - y) >=0 && (yCentre - x) >= 0 && (xCentre - y) < ScreenXsize && (yCentre - x) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre - y, yCentre - x);
        if((xCentre - x) >=0 && (yCentre - y) >= 0 && (xCentre - x) < ScreenXsize && (yCentre - y) < ScreenYsize)
            TFT_DrawPixel(colour, xCentre - x, yCentre - y);

        if (d < 0) d  = (4 * x)   6;
        else
        {
            d  = (4 * (x - y))   10;
            y -= 1;
        }
        x  ;
    }
}

Then let modify it to check if we are in the clipping area:

typedef struct
{
    int32_t xStart, xEnd;
    int32_t yStart, yEnd;
}clip_type;

void GUI_Circle(int32_t xCentre, int32_t yCentre, int32_t radius, clip_type *c, uint32_t colour)
{
    int32_t x = 0, y = radius;
    int32_t d = 3 - (2 * radius);
    clip_type sc = *c;

    if (colour == UINT32_MAX) return;

    if(sc.xEnd - sc.xStart <= 0 || sc.yEnd - sc.yStart <= 0) return;
    if(sc.xEnd < 0 || sc.yEnd < 0) return;
    if(sc.xStart >= ScreenXsize || sc.yStart >= ScreenYsize) return;

    if(sc.xStart < 0) sc.xStart = 0;
    if(sc.yStart < 0) sc.yStart = 0;
    if(sc.xEnd >= ScreenXsize) sc.xEnd = ScreenXsize;
    if(sc.yEnd >= ScreenYsize) sc.yEnd = ScreenYsize;


    while(x <= y)
    {
        //right bottom
        if((xCentre   x) >= sc.xStart && (yCentre   y) >= sc.yStart && (xCentre   x) < sc.xEnd && (yCentre   y) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre   x, yCentre   y);
        if((xCentre   y) >= sc.xStart && (yCentre   x) >= sc.yStart && (xCentre   y) < sc.xEnd && (yCentre   x) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre   y, yCentre   x);

        //left bottom
        if((xCentre - x) >= sc.xStart && (yCentre   y) >= sc.yStart && (xCentre - x) < sc.xEnd && (yCentre   y) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre - x, yCentre   y);
        if((xCentre - y) >= sc.xStart && (yCentre   x) >= sc.yStart && (xCentre - y) < sc.xEnd && (yCentre   x) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre - y, yCentre   x);

        //Top right
        if((xCentre   y) >=sc.xStart && (yCentre - x) >= sc.yStart && (xCentre   y) < sc.xEnd && (yCentre - x) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre   y, yCentre - x);
        if((xCentre   x) >=sc.xStart && (yCentre - y) >= sc.yStart && (xCentre   x) < sc.xEnd && (yCentre - y) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre   x, yCentre - y);

        // Top left
        if((xCentre - y) >= sc.xStart && (yCentre - x) >= sc.yStart && (xCentre - y) < sc.xEnd && (yCentre - x) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre - y, yCentre - x);
        if((xCentre - x) >= sc.xStart && (yCentre - y) >= sc.yStart && (xCentre - x) < sc.xEnd && (yCentre - y) < sc.yEnd)
            TFT_DrawPixel(colour, xCentre - x, yCentre - y);

        if (d < 0) d  = (4 * x)   6;
        else
        {
            d  = (4 * (x - y))   10;
            y -= 1;
        }
        x  ;
    }
}