Question

我的问题对你来说可能很容易。

我正在尝试在我的照片编辑应用中为UIImage添加白色边框。我找到了一些问题和答案How can i take an UIImage and give it a black border?。

大多数答案都是为UIImageView添加边框。在我的情况下，我需要为UIImage添加一个边框宽度可调的边框。

你能帮我吗？

Answer 1

您可以通过访问UIImageView的图层属性来设置CALayer上的边框属性。

首先，添加Quartz

#import <QuartzCore/QuartzCore.h>

设置属性：

[[yourImageView layer] setBorderWidth:2.0f];
[[yourImageView layer] setBorderColor:[UIColor whiteColor].CGColor];

编辑1

由于您需要使用边框保存图像，请使用以下内容。

- (UIImage *)addBorderToImage:(UIImage *)image {
    CGImageRef bgimage = [image CGImage];
    float width = CGImageGetWidth(bgimage);
    float height = CGImageGetHeight(bgimage);

        // Create a temporary texture data buffer
    void *data = malloc(width * height * 4);

    // Draw image to buffer
    CGContextRef ctx = CGBitmapContextCreate(data,
                                                 width,
                                                 height,
                                                 8,
                                                 width * 4,
                                                 CGImageGetColorSpace(image.CGImage),
                                                 kCGImageAlphaPremultipliedLast);
    CGContextDrawImage(ctx, CGRectMake(0, 0, (CGFloat)width, (CGFloat)height), bgimage);

    //Set the stroke (pen) color
    CGContextSetStrokeColorWithColor(ctx, [UIColor greenColor].CGColor);

    //Set the width of the pen mark
    CGFloat borderWidth = (float)width*0.05;
    CGContextSetLineWidth(ctx, borderWidth);

    //Start at 0,0 and draw a square
    CGContextMoveToPoint(ctx, 0.0, 0.0);    
    CGContextAddLineToPoint(ctx, 0.0, height);
    CGContextAddLineToPoint(ctx, width, height);
    CGContextAddLineToPoint(ctx, width, 0.0);
    CGContextAddLineToPoint(ctx, 0.0, 0.0);

    //Draw it
    CGContextStrokePath(ctx);

        // write it to a new image
    CGImageRef cgimage = CGBitmapContextCreateImage(ctx);
    UIImage *newImage = [UIImage imageWithCGImage:cgimage];
    CFRelease(cgimage);
    CGContextRelease(ctx);

        // auto-released
    return newImage;
}

Reference

Answer 2

您需要创建一个新的上下文，然后将图像重新绘制到：

UIImage *image = yourImage;
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[image drawAtPoint:CGPointZero];
[[UIColor whiteColor] setStroke];
UIRectFrame(CGRectMake(0, 0, image.size.width, image.size.height));
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

UIRectFrame绘制1点边框。如果您需要更多，则需要使用UIBezierPath。

UIImage *image = yourImage;
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);
[image drawAtPoint:CGPointZero];
[[UIColor whiteColor] setStroke];
UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, image.size.width, image.size.height)];
path.lineWidth = 2.0;
[path stroke];
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

要在UIImage上作为类别进行完整实施：

<强>的UIImage + Bordered.h

@interface UIImage (Bordered)

-(UIImage *)imageBorderedWithColor:(UIColor *)color borderWidth:(CGFloat)width;

@end

<强>的UIImage + Bordered.m

@implementation UIImage (Bordered)

-(UIImage *)imageBorderedWithColor:(UIColor *)color borderWidth:(CGFloat)width
{
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    [self drawAtPoint:CGPointZero];
    [color setStroke];
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, self.size.width, self.size.height)];
    path.lineWidth = width;
    [path stroke];
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return result;
}

@end

然后使用它就像：

一样简单

UIImage *image = yourImage;
UIImage *borderedImage = [image imageBorderedWithColor:[UIColor whiteColor] borderWidth:2.0];

为UIImage添加白色边框

2 个答案:

编辑1