如何在Objective-C中删除填充图像为红色的UIColor

// Step 1: 加载图像
UIImage *image = [UIImage imageNamed:@"image.png"];

// Step 2: 创建图形上下文
UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale);

// Step 3: 绘制图像
[image drawInRect:CGRectMake(0, 0, image.size.width, image.size.height)];

// Step 4: 获取图像数据
CGContextRef context = UIGraphicsGetCurrentContext();
CGImageRef cgImage = CGBitmapContextCreateImage(context);
CFDataRef data = CGDataProviderCopyData(CGImageGetDataProvider(cgImage));
UInt8 *pixelData = (UInt8 *)CFDataGetBytePtr(data);

// Step 5: 修改图像数据
int length = image.size.width * image.size.height * 4; // 每个像素4个字节（RGBA）
for (int i = 0; i < length; i += 4) {
    UInt8 red = pixelData[i];
    UInt8 green = pixelData[i + 1];
    UInt8 blue = pixelData[i + 2];
    UInt8 alpha = pixelData[i + 3];
    
    if (red == 255 && green == 0 && blue == 0) { // 判断填充颜色为红色
        pixelData[i + 3] = 0; // 将透明度设置为0，即删除填充
    }
}

// Step 6: 创建修改后的图像
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, pixelData, length, NULL);
CGImageRef modifiedImageRef = CGImageCreate(image.size.width, image.size.height, 8, 32, image.size.width * 4, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big, provider, NULL, NO, kCGRenderingIntentDefault);
UIImage *modifiedImage = [UIImage imageWithCGImage:modifiedImageRef];

// Step 7: 结束图形上下文
UIGraphicsEndImageContext();

// 清理内存
CGImageRelease(cgImage);
CFRelease(data);
CFRelease(provider);
CGImageRelease(modifiedImageRef);

// 使用修改后的图像
// ...