iOS Rect相关的重要方法

Rectangle常用工具

通过Points和Sizes创建CGRect

CGRect RectMakeRect(CGPoint origin, CGSize size) {
    return (CGRect){.origin = origin, .size = size}; 
}

获取一个Rectangle中心Point

CGPoint RectGetCenter(CGRect rect) {
    return CGPointMake(CGRectGetMidX(rect), CGRectGetMidY(rect));
}

围绕一个目标Point创建一个Rectangle

CGRect RectAroundCenter(CGPoint center, CGSize size){
    CGFloat halfWidth = size.width / 2.0f;
    CGFloat halfHeight = size.height / 2.0f;
    return CGRectMake(center.x - halfWidth,center.y - halfHeight, size.width, size.height);
}

将一个rect放在另外一个rect的中心

CGRect RectCenteredInRect(CGRect rect, CGRect mainRect) {
    CGFloat dx = CGRectGetMidX(mainRect) - CGRectGetMidX(rect); 
    CGFloat dy = CGRectGetMidY(mainRect) - CGRectGetMidY(rect); 
    return CGRectOffset(rect, dx, dy);
}

Fitting and Filling

Centering

居中显示,会保持原图片的默认的scale,不会放大或者缩小原图.如果图片比显示区域小,那么会在图片周边留白,如果图片比显示区域大,那么图片大小不会变,超出显示区域会直接crop.默认使用这个方法!!!

CGRect RectAroundCenter(CGPoint center, CGSize size){
    CGFloat halfWidth = size.width / 2.0f;
    CGFloat halfHeight = size.height / 2.0f;
    return CGRectMake(center.x - halfWidth,center.y - halfHeight, size.width, size.height);
}

Fitting

当我们使用fit方式显示到目标区域,就需要保存图片所有的内容.根据原始的aspect ratio,图片缩放以后可能是letterboxed或者pillarboxed,然后横向或者纵向有留白.这部分留白内容称为matting.Calculating a Destination by Fitting to a Rectangle:

// Multiply the size components by the factor
CGSize SizeScaleByFactor(CGSize aSize, CGFloat factor) {
    return CGSizeMake(aSize.width * factor, aSize.height * factor);
}


// Calculate scale for fitting a size to a destination
CGFloat AspectScaleFit(CGSize sourceSize, CGRect destRect) {
    CGSize destSize = destRect.size;
    CGFloat scaleW = destSize.width / sourceSize.width;
    CGFloat scaleH = destSize.height / sourceSize.height; 
    return MIN(scaleW, scaleH);
}

// Return a rect fitting a source to a destination 
CGRect RectByFittingInRect(CGRect sourceRect, CGRect destinationRect) {
    CGFloat aspect = AspectScaleFit(sourceRect.size, destinationRect);
    CGSize targetSize = SizeScaleByFactor(sourceRect.size, aspect);
    return RectAroundCenter( RectGetCenter(destinationRect), targetSize);
}

Filling

前面讲到Fitting会在两边有留白.那么如果需要将图片全部填满目标区域,同时保持aspect ratio不变,那么使用filling方式 -- 一般是将soruce rectangle拉升到刚刚好覆盖dest rectangle,然后crop掉超出dest rectangle的部分.总之肯定会crop一部分(有可能是左右部分.或者上下部分)

// Calculate scale for filling a destination
CGFloat AspectScaleFill(CGSize sourceSize, CGRect destRect) {
    CGSize destSize = destRect.size;
    CGFloat scaleW = destSize.width / sourceSize.width; 
    CGFloat scaleH = destSize.height / sourceSize.height;
    return MAX(scaleW, scaleH);
}

// Return a rect that fills the destination
CGRect RectByFillingRect(CGRect sourceRect, CGRect destinationRect) {
    CGFloat aspect = AspectScaleFill(sourceRect.size, destinationRect);
    CGSize targetSize = SizeScaleByFactor(sourceRect.size, aspect);
    return RectAroundCenter(RectGetCenter(destinationRect), targetSize);
}

Squeezing

最后一种常用的显示图片到目标区域的方法是拉伸..不过很少用这种方法