private function _writeCurve()
{
$px = $py = 0;
// 曲线前部分
$A = mt_rand(1, $this->imageH / 2);
// 振幅
$b = mt_rand(-$this->imageH / 4, $this->imageH / 4);
// Y轴方向偏移量
$f = mt_rand(-$this->imageH / 4, $this->imageH / 4);
// X轴方向偏移量
$T = mt_rand($this->imageH, $this->imageW * 2);
// 周期
$w = 2 * M_PI / $T;
$px1 = 0;
// 曲线横坐标起始位置
$px2 = mt_rand($this->imageW / 2, $this->imageW * 0.8);
// 曲线横坐标结束位置
for ($px = $px1; $px <= $px2; $px = $px + 1) {
if (0 != $w) {
$py = $A * sin($w * $px + $f) + $b + $this->imageH / 2;
// y = Asin(ωx+φ) + b
$i = (int) ($this->fontSize / 5);
while ($i > 0) {
imagesetpixel($this->_image, $px + $i, $py + $i, $this->_color);
// 这里(while)循环画像素点比imagettftext和imagestring用字体大小一次画出(不用这while循环)性能要好很多
$i--;
}
}
}
// 曲线后部分
$A = mt_rand(1, $this->imageH / 2);
// 振幅
$f = mt_rand(-$this->imageH / 4, $this->imageH / 4);
// X轴方向偏移量
$T = mt_rand($this->imageH, $this->imageW * 2);
// 周期
$w = 2 * M_PI / $T;
$b = $py - $A * sin($w * $px + $f) - $this->imageH / 2;
$px1 = $px2;
$px2 = $this->imageW;
for ($px = $px1; $px <= $px2; $px = $px + 1) {
if (0 != $w) {
$py = $A * sin($w * $px + $f) + $b + $this->imageH / 2;
// y = Asin(ωx+φ) + b
$i = (int) ($this->fontSize / 5);
while ($i > 0) {
imagesetpixel($this->_image, $px + $i, $py + $i, $this->_color);
$i--;
}
}
}
}