cocoa touch——UIImage——attribute，draw

最新推荐文章于 2018-10-24 17:48:55 发布

mardax

最新推荐文章于 2018-10-24 17:48:55 发布

阅读量318

点赞数

CC 4.0 BY-SA版权

分类专栏： uikit 文章标签： UIImage imageOrientation scale size draw

本文链接：https://blog.youkuaiyun.com/mardax/article/details/52390111

uikit 专栏收录该内容

59 篇文章

订阅专栏

本文详细介绍了UIImage类中的关键属性如imageOrientation、scale及size等，并解释了这些属性如何影响图片的显示效果。此外，还阐述了UIImage的几种常见绘制方法及其参数设置。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

attribute

@property(nonatomic,readonly) UIImageOrientation imageOrientation; // this will affect how the image is composited
@property(nonatomic,readonly) CGFloat scale NS_AVAILABLE_IOS(4_0);
@property(nonatomic,readonly) CGSize size; // reflects orientation setting. In iOS 4.0 and later, this is measured in points. In 3.x and earlier, measured in pixels

typedef NS_ENUM(NSInteger, UIImageOrientation) {
    UIImageOrientationUp,            // default orientation
    UIImageOrientationDown,          // 180 deg rotation
    UIImageOrientationLeft,          // 90 deg CCW
    UIImageOrientationRight,         // 90 deg CW
    UIImageOrientationUpMirrored,    // as above but image mirrored along other axis. horizontal flip
    UIImageOrientationDownMirrored,  // horizontal flip
    UIImageOrientationLeftMirrored,  // vertical flip
    UIImageOrientationRightMirrored, // vertical flip
};

注意：

size是逻辑点size，size跟imageOrientation相关，size * scale为像素点尺寸，同一张图片像素点尺寸不变下，scale变化，size也会相应变化
从bundle的image中加载图片时，如果name中含“@2x”，scale就初始化为2，含“@3x”，scale就初始化为3，只能识别@2x和@3x，其他值会引起错误

draw

// the these draw the image 'right side up' in the usual coordinate system with 'point' being the top-left.

- (void)drawAtPoint:(CGPoint)point;                                                        // mode = kCGBlendModeNormal, alpha = 1.0
- (void)drawAtPoint:(CGPoint)point blendMode:(CGBlendMode)blendMode alpha:(CGFloat)alpha;
- (void)drawInRect:(CGRect)rect;                                                           // mode = kCGBlendModeNormal, alpha = 1.0
- (void)drawInRect:(CGRect)rect blendMode:(CGBlendMode)blendMode alpha:(CGFloat)alpha;

- (void)drawAsPatternInRect:(CGRect)rect; // draws the image as a CGPattern