objective-c - 如何将 UIImage 添加到分组的 UITableViewCell，使其圆角？

Question

我正在尝试将图像添加到分组的 UITableView 中的表格单元格，但图像的角没有被剪裁。剪切这些内容的最佳方法是什么(除了在 Photoshop 中剪切它们之外？表格内容是动态的。)

例如，表格中的第一张图片只需要圆化左上角。

Answer 1

这是我的解决方案，可以使用一些重构:

void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth, float ovalHeight, BOOL top, BOOL bottom)
{
    float fw, fh;
    if (ovalWidth == 0 || ovalHeight == 0) {
        CGContextAddRect(context, rect);
        return;
    }
    CGContextSaveGState(context);
    CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
    CGContextScaleCTM (context, ovalWidth, ovalHeight);
    fw = CGRectGetWidth (rect) / ovalWidth;
    fh = CGRectGetHeight (rect) / ovalHeight;
    CGContextMoveToPoint(context, fw, fh/2);
    CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 0);

    NSLog(@"bottom? %d", bottom);

    if (top) {
        CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 3);
    } else {
        CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 0);
    }

    if (bottom) {
        CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 3);
    } else {
        CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 0);
    }

    CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 0);
    CGContextClosePath(context);
    CGContextRestoreGState(context);
}

- (UIImage *)roundCornersOfImage:(UIImage *)source roundTop:(BOOL)top roundBottom:(BOOL)bottom {
    int w = source.size.width;
    int h = source.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);

    CGContextBeginPath(context);
    CGRect rect = CGRectMake(0, 0, w, h);
    addRoundedRectToPath(context, rect, 4, 4, top, bottom);
    CGContextClosePath(context);
    CGContextClip(context);

    CGContextDrawImage(context, CGRectMake(0, 0, w, h), source.CGImage);

    CGImageRef imageMasked = CGBitmapContextCreateImage(context);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    return [UIImage imageWithCGImage:imageMasked];    
}

实现这些函数，然后检查 cellForRowAtIndexPath 委托(delegate)方法中的 indexPath 以确定圆角。

if (indexPath.row == 0) {
            cell.imageView.image = [self roundCornersOfImage:coverImage roundTop:YES roundBottom:NO];
        } else if (indexPath.row == [indexPath length]) {
            cell.imageView.image = [self roundCornersOfImage:coverImage roundTop:NO roundBottom:YES];
        } else {
            cell.imageView.image = coverImage;
        }