Question

我使用GPUImage框架来获取某些相机输入的平均红色值。我将所有平均红色值存储在一个数组中，我试着这样做：

NSMutableArray *redValues = [NSMutableArray array];
__block int counter = 0;

GPUImageVideoCamera *videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:AVCaptureDevicePositionBack];
videoCamera.outputImageOrientation = UIInterfaceOrientationPortrait;

GPUImageAverageColor *averageColor = [[GPUImageAverageColor alloc] init];
[averageColor setColorAverageProcessingFinishedBlock:^(CGFloat redComponent, CGFloat greenComponent, CGFloat blueComponent, CGFloat alphaComponent, CMTime frameTime)
 {
     NSLog(@"%f", redComponent);
     [redValues addObject:@(redComponent)];         
     counter++;
 }];

for (int i = 0; i < counter; i++)
{
    redValues[i] *= 255; // errors occurs here
}

Answer 1

您得到的错误是因为您试图将NSNumber乘以int。但是，存在一个更深层次的逻辑问题，即您将redComponent作为0到1之间的值接收。当您转换为int时，几乎将所有值都截断为0（此时乘以255将无济于事）。相反，你应该内联乘法（并消除第二个循环）：

averageColor.colorAverageProcessingFinishedBlock = ^(CGFloat redComponent, CGFloat greenComponent, CGFloat blueComponent, CGFloat alphaComponent, CMTime frameTime) {
     NSLog(@"%f", redComponent);
     [redValues addObject:@(redComponent * 255)];
};

二进制表达式的操作数无效（＆＃34; id＆＃34;和＆＃34; int＆＃34;）

1 个答案: