CAEmitterLayer:在CAEmitterCell中使用@2x (视网膜) png图像

Question

使用CAEmitterLayer，@2x (视网膜)图像不会像iOS中的其他地方那样被缩放。我得到的结果是@2x版本是非视网膜图像的4倍大小，而不是缩小。

你知道怎么解决这个问题吗？我已经尝试过在UIImageView中测试图像痛点，结果和它们应该的一样，所以这似乎是CAEmitterLayer和CAEmitterCell的问题。图像具有正确的@2x.png说明符。

下面是我使用的代码：

CAEmitterLayer *fallingCoinEmitter = [CAEmitterLayer layer];
fallingCoinEmitter.emitterPosition = CGPointMake(self.view.bounds.size.width / 2.0, -30);
fallingCoinEmitter.emitterSize = CGSizeMake(self.view.bounds.size.width * 2.0, 0.0);;

    // Spawn points for the flakes are within on the outline of the line
fallingCoinEmitter.emitterMode  = kCAEmitterLayerOutline;
fallingCoinEmitter.emitterShape = kCAEmitterLayerLine;

    // Configure the snowflake emitter cell
CAEmitterCell *coin = [CAEmitterCell emitterCell];
coin.birthRate      = 8.0;
coin.lifetime       = 5.0;
coin.velocity       = -180;             // falling down slowly
coin.velocityRange = 80;
coin.yAcceleration = 40;
coin.emissionRange = 0.4 * M_PI;        // some variation in angle
coin.spinRange      = 0.45 * M_PI;      // slow spin
coin.contents       = (id) [[UIImage imageNamed:@"Coin_Generic_Emitter"] CGImage];
coin.scale          = 1.0;
coin.scaleRange     = 0.0;

    // Make the flakes seem inset in the background
fallingCoinEmitter.shadowOpacity = 1.0;
fallingCoinEmitter.shadowRadius  = 4.0;
fallingCoinEmitter.shadowOffset  = CGSizeMake(0.0, 3.0);
UIColor *darkGreenColor = [UIColor colorWithRed:0.005 green:0.163 blue:0.005 alpha:1.000];
fallingCoinEmitter.shadowColor   = [darkGreenColor CGColor];
[fallingCoinEmitter setContentsScale:[UIScreen mainScreen].scale];
//fallingCoinEmitter.shouldRasterize = YES;
//[fallingCoinEmitter setRasterizationScale:[UIScreen mainScreen].scale];
//fallingCoinEmitter.scale = fallingCoinEmitter.scale / [[UIScreen mainScreen] scale];

    // Add everything to our backing layer below the UIContol defined in the storyboard
fallingCoinEmitter.emitterCells = [NSArray arrayWithObject:coin];
[self.view.layer insertSublayer:fallingCoinEmitter atIndex:0];

谢谢!

更新：

@Fabian，设置contentScale不起作用，至少不是我的解决方案

    [fallingCoinEmitter setContentsScale:[UIScreen mainScreen].scale];

我也试过了，但没有结果。

    emitter.shouldRasterize = YES;
    [emitter setRasterizationScale:[UIScreen mainScreen].scale];

并且设置比例范围不起作用。iPad 2和3的尺寸还是有区别的。

Answer 1

您应该尝试根据设备屏幕修改CAEmmitterCell的scale和scaleRange属性。

cell.scale = cell.scale / [[UIScreen mainScreen] scale];