小编g3k*_*3k0的帖子

使用canvas渲染器,我使用的是绘制线性渐变的函数.我希望这也适用于webgl渲染器,但它会在透明度上窒息.代码在下面,这里是一个小提琴的链接,它表明了我的意思.

function generateTexture() {

var size = 512;

// create canvas
canvas = document.createElement( 'canvas' );
canvas.width = size;
canvas.height = size;

// get context
var context = canvas.getContext( '2d' );

// draw gradient
context.rect( 0, 0, size, size );
var gradient = context.createLinearGradient( 0, 0, size, size );
gradient.addColorStop(0, '#99ddff'); // light blue 
gradient.addColorStop(1, 'transparent');
context.fillStyle = gradient;
context.fill();

return canvas;

}

我正在为视图添加子视图,我希望它填充视图的高度和宽度.我对约束有困难.任何帮助表示赞赏.这就是我目前所拥有的:

    self.view.addSubview(self.mainView)

    var leftSideConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1.0, constant: 0.0)
    var bottomConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Bottom, relatedBy: .Equal, toItem: self.view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
    var widthConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Width, relatedBy: .Equal, toItem: self.view, attribute: .Width, multiplier: 1.0, constant: 0.0)
    var heightConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Height, relatedBy: .Equal, toItem: self.view, attribute: .Height, multiplier: 1.0, constant: 0.0)
    self.view.addConstraints([leftSideConstraint, bottomConstraint, widthConstraint, heightConstraint])