Question

我正在尝试检索主要包含特定颜色的图像。但我的方法并不总能找到具有特定颜色的图像，有时也会找到白色图像。

- (UIColor *)getAvgColorFromUIImage:(UIImage *)image
{
    NSUInteger redP = 0;
    NSUInteger greenP = 0;
    NSUInteger blueP = 0;

    struct pixel* pixels = (struct pixel*) calloc(1,
                                              image.size.width * image.size.height *   sizeof(struct pixel));
    if (pixels != nil)
    {
        CGContextRef context = CGBitmapContextCreate((void *) pixels,
                                                 image.size.width,
                                                 image.size.height,
                                                 8, image.size.width * 4,
                                                 CGImageGetColorSpace(image.CGImage),
                                                 (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
    if (context != NULL)
    {
        CGContextDrawImage(context,
                           CGRectMake(0, 0, image.size.width, image.size.height),
                           image.CGImage);

        NSUInteger numberOfPixels = image.size.width * image.size.height;

        struct pixel* ptr = pixels;

        while (numberOfPixels > 0)
        {
            if (ptr->r > 125)   redP++;
            if (ptr->g > 125)   greenP++;
            if (ptr->b > 125)   blueP++;

            ptr++;
            numberOfPixels--;
        }
        CGContextRelease(context);
    }
    free(pixels);
}

return [UIColor colorWithRed:redP/(image.size.width * image.size.height)
                       green:greenP/(image.size.width * image.size.height)
                        blue:blueP/(image.size.width * image.size.height)
                       alpha:1.0f];
}

以下是用户给定颜色的相似性检查：

- (BOOL)compareUIColor:(UIColor *)a to:(UIColor *)b
{   
CGColorRef iref = [a CGColor];
CGColorRef irefb = [b CGColor];

if (CGColorGetColorSpace(iref) != CGColorGetColorSpace(irefb))  return FALSE;

size_t componentCount = CGColorGetNumberOfComponents(iref);

const double *comp = CGColorGetComponents(iref);
const double *compb = CGColorGetComponents(irefb);

for (int i = 0; i < componentCount; i++)
{
    float difference = comp[i] / compb[i];
    if (fabs(difference - 1) > self.tolerance)   
        return FALSE;
}
return TRUE;
}

你能建议我如何改善这个吗？

此致 WA

Answer 1

如果您尝试按亮度阈值并且仅尝试高于特定亮度的平均颜色，则可以执行以下操作：

NSUInteger weight = 0;
while (numberOfPixels > 0)
{
    uint8_t luminance = (uint8_t)((float)ptr->r * 0.2125 + (float)ptr->g * 0.7152 + (float)ptr->b * 0.0722);
    if (luminance > 125)
    {
        redP += ptr->r;
        greenP += ptr->g;
        blueP += ptr->b;
        weight++;
    }
    ptr++;
    numberOfPixels--;
}
struct pixel average = {redP / weight, greenP / weight, blueP / weight };

平均颜色检测不正常

1 个答案: