Objective c 具有无效上下文的CoreGraphics drawAtPoint

我对core graphics有点陌生，我保留了一个错误，当我合并它们时，第二个图像没有显示出来：

- (UIImage*)imageByCombiningImage:(UIImage*)gfirstImage withImage:(UIImage*)gsecondImage atPositionX:(int)xPosition withPositionY:(int)yPosition{

    UIImage *firstImage = nil;
    UIImage *secondImage = nil;

    firstImage = gfirstImage;
    secondImage = gsecondImage;

    // int ratio = secondImage.size.height/secondImage.size.width;
    // int newWidth = firstImage.size.width/3;
    // int newHeight = (firstImage.size.height/3)*ratio;
    CGSize scaledSize = CGSizeMake(firstImage.size.width, firstImage.size.height);
    CGSize badgeScaledSize = scaledSize;
    if(firstImage.size.width > 500){
        scaledSize = CGSizeMake(firstImage.size.width/4, firstImage.size.height/3);
    }

    if(firstImage.size.width < firstImage.size.height){
        badgeScaledSize = CGSizeMake((firstImage.size.width/4)*prevPinchScale, (firstImage.size.height/4)*prevPinchScale);
    }

    if(firstImage.size.width > firstImage.size.height){
        badgeScaledSize = CGSizeMake((firstImage.size.width/4)*prevPinchScale, (firstImage.size.height/4)*prevPinchScale);
    }



    secondImage = [secondImage resizedImageWithContentMode:UIViewContentModeScaleAspectFit bounds:badgeScaledSize interpolationQuality:0.5];

    CGSize newImageSize = CGSizeMake(firstImage.size.width, firstImage.size.height);

    UIGraphicsBeginImageContext(newImageSize);

    NSLog(@"first image size width: %f, size height: %f", firstImage.size.width, firstImage.size.height);
    NSLog(@"first image size width: %f, size height: %f", newImageSize.width, newImageSize.height);

    [firstImage drawAtPoint:CGPointMake(0,
                                        0)];


    [secondImage drawAtPoint:CGPointMake(xPosition,
                                         yPosition)];

    UIImage *image = nil;
    image = UIGraphicsGetImageFromCurrentImageContext();

    NSLog(@"got image of width: %f and height: %f", image.size.width, image.size.height);

    UIGraphicsEndImageContext();


    return image;
}

-（UIImage*）图像通过将图像：（UIImage*）gfirstImage与图像：（UIImage*）GSecondimmage在位置X:（int）xPosition与位置Y:（int）yPosition组合而成{
UIImage*firstImage=nil；
UIImage*secondImage=nil；
firstImage=G估计值；
secondImage=gsecondImage；
//int ratio=secondImage.size.height/secondImage.size.width；
//int newWidth=firstImage.size.width/3；
//int newHeight=（firstImage.size.height/3）*比率；
CGSize scaledSize=CGSizeMake（firstImage.size.width，firstImage.size.height）；
CGSize BadgedScaledSize=scaledSize；
如果（firstImage.size.width>500）{
scaledSize=CGSizeMake（firstImage.size.width/4，firstImage.size.height/3）；
}
if（firstImage.size.widthfirstImage.size.height）{
badgeScaledSize=CGSizeMake（（firstImage.size.width/4）*prevPinchScale，（firstImage.size.height/4）*prevPinchScale）；
}
secondImage=[secondImage ResizedImage WithContentMode:UIViewContentModeScaleAspectFit界限：badgeScaledSize插值质量：0.5]；
CGSize newImageSize=CGSizeMake（firstImage.size.width，firstImage.size.height）；
UIGraphicsBeginImageContext（newImageSize）；
NSLog（@“第一个图像大小宽度：%f，大小高度：%f”，firstImage.size.width，firstImage.size.height）；
NSLog（@“第一个图像大小宽度：%f，大小高度：%f”，newImageSize.width，newImageSize.height）；
[firstImage drawAtPoint:CGPointMake（0，
0)];
[Second Image drawAtPoint:CGPointMake（xPosition，
位置]；
UIImage*image=nil；
image=UIGraphicsGetImageFromCurrentImageContext（）；
NSLog（@“已获取宽度为%f，高度为%f的图像”，image.size.width，image.size.height）；
UIGraphicsSendImageContext（）；
返回图像；
}

错误如下：

 <Error>: CGContextConcatCTM: invalid context 0x0
 <Error>: CGContextSetInterpolationQuality: invalid context 0x0
 <Error>: CGContextDrawImage: invalid context 0x0
 <Error>: CGBitmapContextCreateImage: invalid context 0x0

：CGContextConcatCTM:无效的上下文0x0
：CGContextSetInterpolationQuality:无效的上下文0x0
：CGContextDrawImage:无效的上下文0x0
：CGBitmapContextCreateImage:无效的上下文0x0

这些错误实际上不是从代码中抛出的，而是在UIImage+Resize.m中抛出的。我假设您正在使用。如果删除该行，代码运行正常

secondImage = [secondImage resizedImageWithContentMode:UIViewContentModeScaleAspectFit bounds:badgeScaledSize interpolationQuality:0.5];

如果您查看该方法，您会发现它调用了另一个方法，该方法进行了四次调用，您将从中获得错误

- (UIImage *)resizedImage:(CGSize)newSize
            transform:(CGAffineTransform)transform
       drawTransposed:(BOOL)transpose
 interpolationQuality:(CGInterpolationQuality)quality {
CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
CGImageRef imageRef = self.CGImage;

// Build a context that's the same dimensions as the new size
CGContextRef bitmap = CGBitmapContextCreate(NULL,
                                            newRect.size.width,
                                            newRect.size.height,
                                            CGImageGetBitsPerComponent(imageRef),
                                            0,
                                            CGImageGetColorSpace(imageRef),
                                            CGImageGetBitmapInfo(imageRef));

// Rotate and/or flip the image if required by its orientation
CGContextConcatCTM(bitmap, transform);

// Set the quality level to use when rescaling
CGContextSetInterpolationQuality(bitmap, quality);

// Draw into the context; this scales the image
CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);

// Get the resized image from the context and a UIImage
CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

// Clean up
CGContextRelease(bitmap);
CGImageRelease(newImageRef);

return newImage;
}

位图的值似乎无效。我将检查以确保在CGBitmapContextCreate调用上，您正在传递实际值，而不是创建大小为0x0的上下文