iphone - UIImageView 适合宽度

Question

我有一个 UIImageView，它位于 UIScrollView 中。 ImageView 中的图像比 iPhone 的屏幕大。我想要做的是按比例缩放图像以适应屏幕宽度，而不改变图像的纵横比(部分图像将在底部脱离屏幕)。

我试过使用 UIViewContentModeScaleAspectFill 和 UIViewContentModeScaleAspectFit 但都没有达到我想要的效果。

有什么想法吗？

谢谢。

Answer 1

这是我编写的一个图像类来执行一些像这样的简单功能，fitInsideWidth 是应该在此处应用的函数:

MyImage.h

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

@interface MyImage : NSObject

+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width covertToHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image convertToHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width;
+ (UIImage*)imageWithImage:(UIImage *)image fitInsideWidth:(float)width fitInsideHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image fitOutsideWidth:(float)width fitOutsideHeight:(float)height;
+ (UIImage*)imageWithImage:(UIImage *)image cropToWidth:(float)width cropToHeight:(float)height;

@end

MyImage.m

#import "MyImage.h"

@implementation MyImage

+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width covertToHeight:(float)height {
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage * newimage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newimage;
}

+ (UIImage*)imageWithImage:(UIImage *)image convertToHeight:(float)height {
    float ratio = image.size.height / height;
    float width = image.size.width / ratio;
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage * newimage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newimage;
}

+ (UIImage*)imageWithImage:(UIImage *)image convertToWidth:(float)width {
    float ratio = image.size.width / width;
    float height = image.size.height / ratio;
    CGSize size = CGSizeMake(width, height);
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage * newimage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newimage;
}

+ (UIImage*)imageWithImage:(UIImage *)image fitInsideWidth:(float)width fitInsideHeight:(float)height {
    if (image.size.height >= image.size.width) {
        return [MyImage imageWithImage:image convertToWidth:width];
    } else {
        return [MyImage imageWithImage:image convertToHeight:height];
    }
}

+ (UIImage*)imageWithImage:(UIImage *)image fitOutsideWidth:(float)width fitOutsideHeight:(float)height {
    if (image.size.height >= image.size.width) {
        return [MyImage imageWithImage:image convertToHeight:height];
    } else {
        return [MyImage imageWithImage:image convertToWidth:width];
    }
}

+ (UIImage*)imageWithImage:(UIImage *)image cropToWidth:(float)width cropToHeight:(float)height {
    CGSize size = [image size];
    CGRect rect = CGRectMake(((size.width-width) / 2.0f), ((size.height-height) / 2.0f), width, height);
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect);
    UIImage * img = [UIImage imageWithCGImage:imageRef]; 
    CGImageRelease(imageRef);
    return img;
}

@end