Format specifies 'unsigned int' but the argument has type 'char*'

Question

I am trying to print the R, G and B value to a label, however It wont print correctly to the label, it just prints the R value with a random set of numbers each time. The error is "Format specifies 'unsigned int' but the argument has type 'char*'

I am new to ios development so help would be appreciated.

  NSLog(@"RGB Value of each pixel:");
  UInt32 * currentPixel = pixels;
  for (NSUInteger j = 0; j < height; j++) {
    for (NSUInteger i = 0; i < width; i++) {
      UInt32 color = *currentPixel;

        printf("(R=%3.0u, G=%3.0u, B=%3.0u) ", R(color), G(color), B(color));

        ERROR HERE >>  _resultLabel.text = [NSString stringWithFormat:@"R= %3.0u", "G= 3.0u", "B= 3.0u", R(color), G(color), B(color)];


        currentPixel++;
    }
    printf("\n");
  }

This gets the pixels of the image

  CGImageRef inputCGImage = [image CGImage];
  NSUInteger width = CGImageGetWidth(inputCGImage);
  NSUInteger height = CGImageGetHeight(inputCGImage);

  NSUInteger bytesPerPixel = 4;
  NSUInteger bytesPerRow = bytesPerPixel * width;
  NSUInteger bitsPerComponent = 8;

  UInt32 * pixels;
  pixels = (UInt32 *) calloc(height * width, sizeof(UInt32));

  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  CGContextRef context = CGBitmapContextCreate(pixels, width, height,
                                               bitsPerComponent, bytesPerRow, colorSpace,
                                               kCGImageAlphaPremultipliedLast|kCGBitmapByteOrder32Big);

  CGContextDrawImage(context, CGRectMake(0, 0, width, height), inputCGImage);

  CGColorSpaceRelease(colorSpace);
  CGContextRelease(context);

#define Mask8(x) ( (x) & 0xFF )
#define R(x) ( Mask8(x) )
#define G(x) ( Mask8(x >> 8 ) )
#define B(x) ( Mask8(x >> 16) )

Here is the image of the output

The error has gone however it just prints out a blank result, Anyone know why?

Answer 1

您正在使用格式说明符，如下所示：

[NSString stringWithFormat:@"R= %3.0u", "G= 3.0u", "B= 3.0u", R(color), G(color), B(color)];

此函数需要在第一个参数中应替换的所有参数。问题是第二个参数。 这是第一个论点。

 @"R= %3.0u"

下一个参数应该是替换％3.0u 的值，下一个参数是字符串＆＃34; G = 3.0u＆＃34; 这就是为什么它会给你警告。用以下代码替换您的代码：

[NSString stringWithFormat:@"R= %3.0u G= %3.0u B= %3.0u", R(color), G(color), B(color)];

然后你很高兴。如需进一步咨询：

https://developer.apple.com/reference/foundation/nsstring/1497275-stringwithformat