在CIImage周围画边框

Question

我正在寻找一种使用 Core Image 添加实心边框的方法。我已经实现了自定义相机来拍摄矩形文档的照片。现在我得到了四个坐标的文档，但在 CIImage 上绘制边界的问题。请帮助我。

 CIImage *overlay = [CIImage imageWithColor:[CIColor colorWithRed:0 green:1 blue:0 alpha:0.6]];
overlay = [overlay imageByCroppingToRect:image.extent];
overlay = [overlay imageByApplyingFilter:@"CIPerspectiveTransformWithExtent" withInputParameters:@{@"inputExtent":[CIVector vectorWithCGRect:image.extent],@"inputTopLeft":[CIVector vectorWithCGPoint:topLeft],@"inputTopRight":[CIVector vectorWithCGPoint:topRight],@"inputBottomLeft":[CIVector vectorWithCGPoint:bottomLeft],@"inputBottomRight":[CIVector vectorWithCGPoint:bottomRight]}];
return [overlay imageByCompositingOverImage:image];

Answer 1

您可以使用此方法：

- (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;
}

调用此方法：

UIImage *updatedIMG = [self addBorderToImage:[[UIImage alloc] initWithCIImage:overlay]]