ios - 我的图像没有被裁剪

Question

我有以下主要从 SO 获得的代码，但我的图像仍然没有被裁剪，我做错了什么？

@synthesize TopImage;
@synthesize BottomImage;
@synthesize RotaterImage;

- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
    TopImage = [UIImage imageNamed:@"zero.png"];
    [TopImage drawAtPoint:CGPointMake(0, 0)];
    [self cropImage:TopImage:0];
    [self addSubview:[[UIImageView alloc] initWithImage:TopImage]];
//        BottomImage = [UIImage imageNamed:@"zero.png"];
//        [BottomImage drawAtPoint:CGPointMake(0, 55)];
//        [self cropImage:BottomImage:50];
//        [self addSubview:[[[UIImageView alloc] initWithImage:BottomImage]retain]];
//        RotaterImage = [UIImage imageNamed:@"zero.png"];
//        [RotaterImage drawAtPoint:CGPointMake(0, 0) blendMode:kCGBlendModeNormal alpha:0];
//        [self addSubview:[[[UIImageView alloc] initWithImage:RotaterImage]retain]];
//        [self cropImage:RotaterImage:50];
    }
    return self;
}

-(void)cropImage:(UIImage *)image:(int)startCroppingPosition{
  CGRect tempRect = CGRectMake(0, startCroppingPosition, 23, 40);
  CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], tempRect);
  // or use the UIImage wherever you like
  image = [UIImage imageWithCGImage:imageRef]; 
  CGImageRelease(imageRef);
}

我是 IOS 的新手，所以感谢任何帮助

Answer 1

你正在创建一个新的裁剪图像但没有告诉 init 方法:)

试试这个改变:

-(UIImage *)cropImage:(UIImage *)image:(int)startCroppingPosition{
  CGRect tempRect = CGRectMake(0, startCroppingPosition, 23, 40);
  CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], tempRect);
  // or use the UIImage wherever you like
  UIImage *newImage = [UIImage imageWithCGImage:imageRef]; 
  CGImageRelease(imageRef);
  return newImage;
}

并且，在 init 中，替换

[TopImage drawAtPoint:CGPointMake(0, 0)];

与

UIImageView* topImageView = [[UIImageView alloc] initWithImage:topImage];
topImageView.frame = CGRectMake(x,y,width,height);

您的裁剪方法现在返回新裁剪的图像并将其存储在 TopImage 中。

---

其他建议:

类名以大写字母开头，变量以小写字母开头。 TopImage 应该是 topImage。

此外，我总是会在您的方法中使用命名参数，所以

-(void)cropImage:(UIImage *)image:(int)startCroppingPosition

应该是这样的

-(void)cropImage:(UIImage *)image startPosition:(int)startCroppingPosition

这将使您的代码在一个月后回过头来时更具可读性(我在过去的艰难过程中学到了这一点!)