Question

我能够成功地重绘具有边框的UIImage，但不能使用边框+阴影。下面的代码成功地绘制了带有白色边框的图像，但我无法弄清楚如何在边框下包含阴影。非常感谢帮助！

- (UIImage *)generatePhotoFrameWithImage:(UIImage *)image {
CGSize newSize = CGSizeMake(image.size.width + 50, image.size.height + 60);
UIGraphicsBeginImageContext(newSize);
CGRect rect = CGRectMake(25, 35, image.size.width, image.size.height);
[image drawInRect:rect blendMode:kCGBlendModeNormal alpha:1.0];

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
CGContextStrokeRectWithWidth(context, CGRectMake(25, 35, image.size.width, image.size.height), 50);

//CGContextSetShadowWithColor(context, CGSizeMake(0, -60), 5, [UIColor blackColor].CGColor);

UIImage *result =  UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return result; }

PS：我没有使用UIImageView，因为我需要保持完整的图像质量。

Answer 1

你需要在划过边框之前调用CGContextSetShadowWithColor，因此边框会投射阴影。

如果您不希望边框在图像上投射阴影，则需要设置一个透明图层，在该图层中绘制图像和边框。您可以在Quartz 2D Programming Guide中了解透明度图层。

如果您想保留图像质量，则需要使用UIGraphicsBeginImageContextWithOptions并传入原始图像的比例。

- (UIImage *)generatePhotoFrameWithImage:(UIImage *)image {
    CGSize newSize = CGSizeMake(image.size.width + 50, image.size.height + 60);
    CGRect rect = CGRectMake(25, 35, image.size.width, image.size.height);

    UIGraphicsBeginImageContextWithOptions(newSize, NO, image.scale); {
        CGContextRef context = UIGraphicsGetCurrentContext();

        CGContextBeginTransparencyLayer(context, NULL); {
            [image drawInRect:rect blendMode:kCGBlendModeNormal alpha:1.0];

            CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
            CGContextSetShadowWithColor(context, CGSizeMake(0, 5), 5, [UIColor blackColor].CGColor);
            CGContextStrokeRectWithWidth(context, CGRectMake(25, 35, image.size.width, image.size.height), 50);
        } CGContextEndTransparencyLayer(context);
    }
    UIImage *result =  UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return result;
}

Answer 2

谢谢Rob给我指出正确的方向。这是在图像周围绘制白色边框的最终代码，然后是边框外侧的浅灰色阴影

- (UIImage *)generatePhotoStackWithImage:(UIImage *)image {
CGSize newSize = CGSizeMake(image.size.width + 70, image.size.height + 70);
CGRect rect = CGRectMake(25, 25, image.size.width, image.size.height);

UIGraphicsBeginImageContextWithOptions(newSize, NO, image.scale); {
    CGContextRef context = UIGraphicsGetCurrentContext();
    //Shadow
    CGContextSetShadowWithColor(context, CGSizeMake(0, 0), 10, [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.5f].CGColor);

    CGContextBeginTransparencyLayer (context, NULL);
    //Draw
    [image drawInRect:rect blendMode:kCGBlendModeNormal alpha:1.0];
    CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
    CGContextStrokeRectWithWidth(context, rect, 40);
    CGContextEndTransparencyLayer(context);
}
UIImage *result =  UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return result;
}

在UIImage上绘制边框和阴影

2 个答案: