一个好的app界面展示,必须要各种图片来填充,用图片去传递一些信息,图片比文字有更好的效果.为此,总结了一下一些image的用法

1.根据颜色生成image

+(UIImage *)imageWithBgColor:(UIColor *)color
{
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

2.修改image的方向

对image的当前方向进行判断,然后进行矩阵转换,生成新的image

if (image.imageOrientation == UIImageOrientationUp)
        return image;
    
    CGAffineTransform transform = CGAffineTransformIdentity;
    
    switch (image.imageOrientation) {
        case UIImageOrientationDown:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, image.size.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;
            
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, 0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;
            
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, image.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
        default:
            break;
    }
    
    switch (image.imageOrientation) {
        case UIImageOrientationUpMirrored:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
            
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.height, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
        default:
            break;
    }

3.多张图片合成一张图片

UIGraphicsBeginImageContext(size);
    for (int i =  0; i < imageArray.count; i++) {
        UIImage *image = imageArray[i];
        NSValue *value = offsetArray[i];
        CGRect rect = [value CGRectValue];
        [image drawInRect:rect];
    }
    
    UIImage *resultingImage =UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

效果图:

图片合成.png

4.image的拉伸

这是是调用系统的方法,其中模式有俩种,一种是拉伸,一种是平铺.

+ (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets image:(UIImage *)image
{
    UIImage *newImage = [image resizableImageWithCapInsets:capInsets resizingMode:UIImageResizingModeStretch];
    return newImage;
}

5.对image进行裁剪

这个效果的话用在头像截取比较好一点,如果图片跟imageView差距不是很大的话,可以改变填充模式来适应view.

if (image.size.width > image.size.height) {
        imageOrientation = UIImageOrientationRight;
        if ((image.size.width / image.size.height) < scale) {
            newSize.width = image.size.width;
            newSize.height = image.size.width * scale;
            
            imageRef = CGImageCreateWithImageInRect([image CGImage], CGRectMake(0, fabs(image.size.height - newSize.height) / 2, newSize.width, newSize.height));
            
        } else {
            newSize.height = image.size.height;
            newSize.width = image.size.height / scale;
            
            imageRef = CGImageCreateWithImageInRect([image CGImage], CGRectMake(fabs(image.size.width - newSize.width) / 2, 0, newSize.width, newSize.height));
        }
    } else {
        imageOrientation = UIImageOrientationUp;
        if ((image.size.width / image.size.height) < scale) {
            newSize.width = image.size.width;
            newSize.height = image.size.width / scale;
            
            imageRef = CGImageCreateWithImageInRect([image CGImage], CGRectMake(0, fabs(image.size.height - newSize.height) / 2, newSize.width, newSize.height));
            
        } else {
            newSize.height = image.size.height;
            newSize.width = image.size.height * scale;
            
            imageRef = CGImageCreateWithImageInRect([image CGImage], CGRectMake(fabs(image.size.width - newSize.width) / 2, 0, newSize.width, newSize.height));
        }
    }

裁剪前.png
裁剪后.png

6.生成带边框的image

+ (UIImage *)imageWithBorderW:(CGFloat)borderW borderColor:(UIColor *)color image:(UIImage *)image
{
    //开启图片大小一样的上下文
    CGSize size = CGSizeMake(image.size.width + 2 *borderW, image.size.height + 2 * borderW);
    UIGraphicsBeginImageContextWithOptions(size,NO,0);
    //添加一个填充区域
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, size.width, size.height)];
    [color set];
    [path fill];
    //添加一个裁剪区域
    path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(borderW, borderW, image.size.width, image.size.height)];
    [path addClip];
    //添加图片到裁剪区域
    [image drawAtPoint:CGPointMake(borderW, borderW)];
    //得到新图片
    UIImage *clipImage = UIGraphicsGetImageFromCurrentImageContext();
    //关闭上下文.
    UIGraphicsEndImageContext();
    return clipImage;
}

附图:

带边框的图.png

7.屏幕截图(可以对任意一个view进行截图)

+ (UIImage *)captureWithView:(UIView *)view
{
    // 1.开启上下文
    UIGraphicsBeginImageContextWithOptions(view.frame.size, NO, 0);
    // 2.将控制器view的layer渲染到上下文
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    // 3.取出图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    // 4.结束上下文
    UIGraphicsEndImageContext();
    return newImage;
}

附图:

截图.png

8.给图片加水印

+ (UIImage *)waterImageWith:(UIImage *)image logo:(UIImage *)logoImage
{
    // 上下文 : 基于位图(bitmap) ,  所有的东西需要绘制到一张新的图片上去
    // 1.创建一个基于位图的上下文(开启一个基于位图的上下文)
    // size : 新图片的尺寸
    // opaque : YES : 不透明,  NO : 透明
    // 这行代码过后.就相当于创建一张新的bitmap,也就是新的UIImage对象
    UIGraphicsBeginImageContextWithOptions(image.size, NO, 0.0);
    
    // 画背景
    [image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];
    
    // 画右下角的水印
    CGFloat scale = 0.2;
    CGFloat logoW = logoImage.size.width * scale;
    CGFloat logoH = logoImage.size.height * scale;
    CGFloat margin = 5;
    CGFloat logoX = image.size.width - logoW - margin;
    CGFloat logoY = image.size.height - logoH - margin;
    CGRect rect = CGRectMake(logoX, logoY, logoW, logoH);
    [logoImage drawInRect:rect];
    // 从上下文中取得制作完毕的UIImage对象
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    // 结束上下文
    UIGraphicsEndImageContext();
    
    return newImage;
}

附图:

水印.png

9.圆角图片处理,解决tableView卡顿问题

/** 设置圆形图片(放到分类中使用) */
- (UIImage *)cutCircleImage {
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
    // 获取上下文
    CGContextRef ctr = UIGraphicsGetCurrentContext();
    // 设置圆形
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGContextAddEllipseInRect(ctr, rect);
    // 裁剪
    CGContextClip(ctr);
    // 将图片画上去
    [self drawInRect:rect];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

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