iOS图像主色提取算法——单像素压缩

总述

这是基于iOS平台的，用Objective-C实现的算法，是一个UIColor的类别。具体做法是，将图片压缩成1个像素点，提取这个像素的颜色，作为该图片的主色。

评价

速度最快，最简单粗暴的做法。

实现

- (UIColor *)getMainColor {
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(1.0f, 1.0f), NO, 1.0f);
    [self drawInRect:CGRectMake(0, 0, 1, 1)];
    UIImage *tempImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    CGImageRef cgTempImage = tempImage.CGImage;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    int bytesPerPixcel = 4;
    int bytesPerRow = bytesPerPixcel * 1;
    NSUInteger bitsPerChannel = 8;
    unsigned char pixelData[4] = {0};
    CGContextRef context = CGBitmapContextCreate(pixelData,
                                                 1,
                                                 1,
                                                 bitsPerChannel,
                                                 bytesPerRow,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);
    CGContextSetBlendMode(context, kCGBlendModeCopy);
    CGContextDrawImage(context, CGRectMake(0, 0, 1, 1), cgTempImage);
    CGContextRelease(context);
    CGFloat redFloat = pixelData[0];
    redFloat /= 255.0f;
    CGFloat greenFloat = pixelData[1];
    greenFloat /= 255.0f;
    CGFloat blueFloat = pixelData[2];
    blueFloat /= 255.0f;
    CGFloat alphaFloat = pixelData[3];
    alphaFloat /= 255.0f;
    return [UIColor colorWithRed:redFloat green:greenFloat blue:blueFloat alpha:alphaFloat];
}

效果