Page 557 - Beginning PHP 5.3

Chapter 17: Generating Images with PHP

of the rectangle that the curve should begin. The last parameter is, of course, the color of the rectangle.
Figure 17-14 shows how the parameters passed to the roundedRectangle() function are used.

Curve depth
x1, y1•

• x2, y2
Figure 17-14

The function first draws the line across the top of the rectangle. It doesn’t draw the line all the way from
$x1 to $x2 because it has to take the curves of the corners into account. To do this it adds the
$curveDepth value to the $x1 position, and subtracts it from the $x2 position:

imageline( $image, ($x1 + $curveDepth), $y1, ($x2 - $curveDepth), $y1,
$color );
Because the line is horizontal, both points use the same y position. The next line goes along the bottom of
the rectangle in a similar fashion:

imageline( $image, ($x1 + $curveDepth), $y2, ($x2 - $curveDepth), $y2,
$color );
The next two lines are the vertical lines that go down the left- and right-hand sides of the rectangle. This
time the function uses the same x values for each of the lines ($x1 for the left-hand line and $x2 for the
right-hand side), and alters the y values appropriately so that the height of the lines fits in with the
curved corners:
imageline( $image, $x1, ($y1 + $curveDepth), $x1, ($y2 - $curveDepth),
$color );
imageline( $image, $x2, ($y1 + $curveDepth), $x2, ($y2 - $curveDepth),
$color );

Next the function draws the curved corners, starting with the top-left corner. In order to calculate the
center point of the arc (see Figure 17-15), the function adds the value of $curveDepth to both the $x1
and the $y1 values. To get the arc’s width and height, the function needs to double the $curveDepth
value, because $curveDepth is actually the radius of the arc.

x1, y1
•

•
Arc center point

Figure 17-15

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