Objective C 操作图像

Question

我想处理图像和随机颜色。我试图用像素旋转 180 度但失败了。我不想使用 UIImageView 旋转因为我不会只旋转图像。我想为所欲为。

编辑：这是错误的运营商。我不知道为什么我使用 % 而不是 / 。无论如何，我希望这段代码可以帮助某人（它有效）。

- (IBAction)shuffleImage:(id)sender {

[self calculateRGBAsAndChangePixels:self.imageView.image atX:0 andY:0];

}

-(void)calculateRGBAsAndChangePixels:(UIImage*)image atX:(int)x andY:(int)y

{


NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * image.size.width;
NSUInteger bitsPerComponent = 8;

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bmContext = CGBitmapContextCreate(NULL, image.size.width, image.size.height, bitsPerComponent,bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextDrawImage(bmContext, (CGRect){.origin.x = 0.0f, .origin.y = 0.0f, image.size.width, image.size.height}, image.CGImage);

UInt8* data = (UInt8*)CGBitmapContextGetData(bmContext);

const size_t bitmapByteCount = bytesPerRow * image.size.height;
NSMutableArray *reds = [[NSMutableArray alloc] init];
NSMutableArray *greens = [[NSMutableArray alloc] init];
NSMutableArray *blues = [[NSMutableArray alloc] init];



for (size_t i = 0; i < bitmapByteCount; i += 4)
{
    [reds addObject:[NSNumber numberWithInt:data[i]]];
    [greens addObject:[NSNumber numberWithInt:data[i+1]]];
    [blues addObject:[NSNumber numberWithInt:data[i+2]]];

}

for (size_t i = 0; i < bitmapByteCount; i += 4)
{

    data[i] = [[reds objectAtIndex:reds.count-i%4-1] integerValue];
    data[i+1] = [[greens objectAtIndex:greens.count-i%4-1] integerValue];
    data[i+2] = [[blues objectAtIndex:blues.count-i%4-1] integerValue];

}

CGImageRef newImage = CGBitmapContextCreateImage(bmContext);
UIImage *imageView = [[UIImage alloc] initWithCGImage:newImage];
self.imageView.image = imageView;
}

Answer 1

因此，您希望实际操作原始像素数据。那就看看吧：

Getting the pixel data from a CGImage object

它适用于 MacOS，但也应该适用于 iOS。

Answer 2

假设您想让图像倒置（将其旋转 180 度）而不是镜像它，我在 another question 上找到了一些可能对您有所帮助的相关代码：

static inline double radians (double degrees) {return degrees * M_PI/180;}
UIImage* rotate(UIImage* src, UIImageOrientation orientation)
{
    UIGraphicsBeginImageContext(src.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    if (orientation == UIImageOrientationRight) {
        CGContextRotateCTM (context, radians(90));
    } else if (orientation == UIImageOrientationLeft) {
        CGContextRotateCTM (context, radians(-90));
    } else if (orientation == UIImageOrientationDown) {
        // NOTHING
    } else if (orientation == UIImageOrientationUp) {
        CGContextRotateCTM (context, radians(90));
    }

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

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

如果您尝试镜像图像，this question 中的此代码示例可能会有所帮助：

UIImage* sourceImage = [UIImage imageNamed:@"whatever.png"];

UIImage* flippedImage = [UIImage imageWithCGImage:sourceImage.CGImage 
                                            scale:sourceImage.scale
                                      orientation:UIImageOrientationUpMirrored];