老司机带你走进Core Animation 之粒子发射、TileLayer与异步绘制

CAEmitterLayer *emitter = [CAEmitterLayer layer];
emitter.frame = self.bgView.bounds;
self.bgView.backgroundColor = [UIColor blackColor];
[self.bgView.layer addSublayer:emitter];
///粒子的产生速率，即每秒产生的个数
emitter.birthRate = 150;
///每个粒子可以停留，也就是显示的时间
emitter.lifetime = 5;
///每个粒子的初速度
emitter.velocity = 50;
///每个粒子的缩放比例
emitter.scale = 0.5;
///每个粒子的旋转角度
emitter.spin = M_PI;
///渲染模式
emitter.renderMode = kCAEmitterLayerBackToFront;
///粒子发生器的位置
emitter.emitterPosition = CGPointMake(emitter.frame.size.width / 2.0, emitter.frame.size.height / 2.0);
///粒子发生器的大小
emitter.emitterSize = CGSizeMake(50, 50);
///粒子发生器的形状
emitter.emitterShape = kCAEmitterLayerLine;
///粒子发射的模式
emitter.emitterMode = kCAEmitterLayerOutline;
self.layer = emitter;

//create a particle template
CAEmitterCell *cell = [[CAEmitterCell alloc] init];
///粒子内容，也就是你要展示的粒子元素
cell.contents = (__bridge id)[UIImage imageNamed:@"爱心"].CGImage;
///粒子的初始颜色
cell.color = [UIColor colorWithRed:0.5 green:0.5 blue:0.5 alpha:1].CGColor;

///同emitterLayer提供的属性具有相同含义，不同的是emitterLayer中的属性更像是乘法器中的一个比例系数，也就是说layer中的对应属性与cell中的属性相乘才是这个属性最终的值。因为layer可以盛放多种类型cell，所以layer中的数值会作用于所有cell，而cell中的数值仅影响自身实例。
cell.lifetime = 1;
cell.birthRate = 1;
cell.velocity = 1;
cell.scale = 1;
cell.spin = 1;

///一些属性的改变速率，设置了对应值后，粒子的属性会按照改变速率进行改变
cell.alphaSpeed = -0.1;
cell.redSpeed = 0.1;
cell.blueSpeed = 0.1;
cell.greenSpeed = 0.1;

///一些属性的扰动范围，所谓扰动范围就是在你设置的固定值两端+-扰动值形成一个范围，那所有粒子的对应属性都在扰动这个范围之内随机产生，这样可以方便产生不同的粒子，而不是千篇一律相同的粒子
cell.alphaRange = 0.8;
cell.scaleRange = 1;
cell.emissionRange = M_PI_4;
cell.redRange = 1;
cell.greenRange = 1;
cell.blueRange = 1;

///粒子发射倾斜的角度
cell.emissionLongitude = M_PI_4;

///粒子y轴运动方向的加速度，相似的还有xAcceleration，通常用来模拟重力加速度，产生粒子坠落的效果
cell.yAcceleration = 100;
self.cell = cell;

///初始化cell后将其放在容器内，容器即可自动产生粒子并进行发射。
//此处注意是一个数组，也就是说你可以把多个粒子实例传入其中。
emitter.emitterCells = @[cell];

+(Class)layerClass
{
    return [CATiledLayer class];
}

-(instancetype)initWithFrame:(CGRect)frame path:(NSString *)path completion:(void (^)(CGSize))completion
{
    self = [super initWithFrame:frame];
    if (self) {
        NSURL *docURL = [NSURL fileURLWithPath:path];
        CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL((CFURLRef)docURL);
        CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);
        self.page = page;
        CGRect pageRect = CGPDFPageGetBoxRect(page, kCGPDFCropBox);
        CATiledLayer * layer = (CATiledLayer *)self.layer;
        layer.levelsOfDetailBias = 5;
        
        layer.bounds = pageRect;
        int w = pageRect.size.width;
        int h = pageRect.size.height;
        
        int levels = 1;
        while (w > 1 && h > 1) {
            levels++;
            w = w >> 1;
            h = h >> 1;
        }
        layer.levelsOfDetail = levels;
        [self setFrame:pageRect];
        if (completion) {
            completion(pageRect.size);
        }
    }
    return self;
}

-(void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx
{
    CGContextDrawPDFPage(ctx, self.page);
}

static dispatch_queue_t DWCoreTextLabelLayerGetDisplayQueue() {
#define MAX_QUEUE_COUNT 16
    static int queueCount;
    static dispatch_queue_t queues[MAX_QUEUE_COUNT];
    static dispatch_once_t onceToken;
    static int32_t counter = 0;
    dispatch_once(&onceToken, ^{
        queueCount = (int)[NSProcessInfo processInfo].activeProcessorCount;
        queueCount = queueCount < 1 ? 1 : queueCount > MAX_QUEUE_COUNT ? MAX_QUEUE_COUNT : queueCount;
        if ([UIDevice currentDevice].systemVersion.floatValue >= 8.0) {
            for (NSUInteger i = 0; i < queueCount; i++) {
                dispatch_queue_attr_t attr = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_USER_INITIATED, 0);
                queues[i] = dispatch_queue_create("com.codeWicky.DWCoreTextLabel.render", attr);
            }
        } else {
            for (NSUInteger i = 0; i < queueCount; i++) {
                queues[i] = dispatch_queue_create("com.codeWicky.DWCoreTextLabel.render", DISPATCH_QUEUE_SERIAL);
                dispatch_set_target_queue(queues[i], dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0));
            }
        }
    });
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    uint32_t cur = (uint32_t)OSAtomicIncrement32(&counter);
#pragma clang diagnostic pop
    return queues[(cur) % queueCount];
#undef MAX_QUEUE_COUNT
}

static dispatch_queue_t DWCoreTextLabelLayerGetReleaseQueue() {
    return dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0);
}

@interface DWAsyncLayer ()

@property (atomic, readonly) int32_t signal;

@end

@implementation DWAsyncLayer

-(instancetype)init
{
    self = [super init];
    if (self) {
        _signal = 0;
        _displaysAsynchronously = YES;
    }
    return self;
}

-(void)signalIncrease
{
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
    OSAtomicIncrement32(&_signal);
#pragma clang diagnostic pop
}

-(void)setNeedsDisplay
{
    [self cancelPreviousDisplayCalculate];
    [super setNeedsDisplay];
}

-(void)cancelPreviousDisplayCalculate
{
    [self signalIncrease];
}

-(void)dealloc
{
    [self cancelPreviousDisplayCalculate];
}

-(void)display
{
    super.contents = super.contents;
    [self displayAsync:self.displaysAsynchronously];
}

-(void)displayAsync:(BOOL)async
{
    if (!self.displayBlock) {
        self.contents = nil;
        return;
    }
    if (async) {
        int32_t signal = self.signal;
        BOOL (^isCancelled)() = ^BOOL() {
            return signal != self.signal;
        };
        CGSize size = self.bounds.size;
        BOOL opaque = self.opaque;
        CGFloat scale = self.contentsScale;
        CGColorRef backgroundColor = (opaque && self.backgroundColor) ? CGColorRetain(self.backgroundColor) : NULL;
        if (size.width < 1 || size.height < 1) {
            CGImageRef image = (__bridge_retained CGImageRef)(self.contents);
            self.contents = nil;
            if (image) {
                dispatch_async(DWCoreTextLabelLayerGetReleaseQueue(), ^{
                    CFRelease(image);
                });
            }
            CGColorRelease(backgroundColor);
            return;
        }
        
        dispatch_async(DWCoreTextLabelLayerGetDisplayQueue(), ^{
            if (isCancelled()) {
                CGColorRelease(backgroundColor);
                return;
            }
            UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
            CGContextRef context = UIGraphicsGetCurrentContext();
            if (opaque) {
                fillContextWithColor(context, backgroundColor, size);
                CGColorRelease(backgroundColor);
            }
            self.displayBlock(context,isCancelled);
            if (isCancelled()) {
                UIGraphicsEndImageContext();
                return;
            }
            UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            if (isCancelled()) {
                return;
            }
            dispatch_async(dispatch_get_main_queue(), ^{
                if (!isCancelled()) {
                    self.contents = (__bridge id)(image.CGImage);
                }
            });
        });
    } else {
        [self signalIncrease];
        UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.opaque, self.contentsScale);
        CGContextRef context = UIGraphicsGetCurrentContext();
        if (self.opaque) {
            CGSize size = self.bounds.size;
            size.width *= self.contentsScale;
            size.height *= self.contentsScale;
            fillContextWithColor(context, self.backgroundColor,size);
        }
        self.displayBlock(context,^{return NO;});
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        self.contents = (__bridge id)(image.CGImage);
    }
}

static inline void fillContextWithColor(CGContextRef context,CGColorRef color,CGSize size){
    CGContextSaveGState(context); {
        if (!color || CGColorGetAlpha(color) < 1) {
            CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
            CGContextAddRect(context, CGRectMake(0, 0, size.width, size.height));
            CGContextFillPath(context);
        }
        if (color) {
            CGContextSetFillColorWithColor(context, color);
            CGContextAddRect(context, CGRectMake(0, 0, size.width, size.height));
            CGContextFillPath(context);
        }
    } CGContextRestoreGState(context);
};

@end