缘起
UIImageView在加载大分辨率图像时，可能无法渲染出来，特别是在模拟器上运行的时候。
可对大图进行切分成一块一块小图，分成多个ImageView加载，然后拼在一起。
实现
JXLargeImageView.h
/// 切分大图，用多个小图来显示。只支持竖直的长图
@interface JXLargeImageView : UIImageView
/// 单块图片最大高度因子，宽度的倍数。默认为5
@property (nonatomic, assign) NSInteger maxHeightFator;
@end
JXLargeImageView.m
- (void)setImage:(UIImage *)image {
_image = image;
[self.imageViewArray enumerateObjectsUsingBlock:^(UIImageView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
[obj removeFromSuperview];
}];
[self.imageViewArray removeAllObjects];
if (!image) {
return;
}
CGFloat imageWidth = image.size.width;
CGFloat maxImageHeight = imageWidth * self.maxHeightFator;
if (maxImageHeight == 0) {
return;
}
NSInteger count = ceil(image.size.height / maxImageHeight);
for (NSInteger index = 0; index < count; ++ index) {
CGFloat height = (index == count - 1) ? image.size.height - maxImageHeight * index : maxImageHeight;
CGImageRef imgRef = CGImageCreateWithImageInRect(image.CGImage, CGRectMake(0, index * maxImageHeight, imageWidth, height));
UIImageView *view = [[UIImageView alloc] initWithImage:[UIImage imageWithCGImage:imgRef]];
view.contentMode = self.contentMode;
[self addSubview:view];
[self.imageViewArray addObject:view];
}
[self setNeedsLayout];
}
- (void)layoutSubviews {
[super layoutSubviews];
CGFloat imageWidth = self.bounds.size.width;
CGFloat maxImageHeight = imageWidth * self.maxHeightFator;
if (maxImageHeight == 0) {
return;
}
NSInteger count = ceil(self.bounds.size.height / maxImageHeight);
[self.imageViewArray enumerateObjectsUsingBlock:^(UIImageView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
CGFloat height = (idx == count - 1) ? self.bounds.size.height - maxImageHeight * idx : maxImageHeight;
obj.frame = CGRectMake(0, idx * maxImageHeight, imageWidth, height);
}];
}
JXLargeImageView
