方法1 CIFilter 滤镜

适合纯色背景，扣图精准

struct CubeMap cubeMap =  createCubeMap(60, 90);
    NSData *data = [NSData dataWithBytesNoCopy:cubeMap.data length:cubeMap.length freeWhenDone:YES];
    CIFilter *colorCubeFilter = [CIFilter filterWithName:@"CIColorCube"];
     
    [colorCubeFilter setValue:[NSNumber numberWithFloat:cubeMap.dimension] forKey:@"inputCubeDimension"];
    [colorCubeFilter setValue:data forKey:@"inputCubeData"];
    [colorCubeFilter setValue:[[CIImage alloc] initWithImage:_iv.image] forKey:kCIInputImageKey];
    CIImage *outputImage = colorCubeFilter.outputImage;
    
    CIFilter *sourceOverCompositingFilter = [CIFilter filterWithName:@"CISourceOverCompositing"];
    
    [sourceOverCompositingFilter setValue:outputImage forKey:kCIInputImageKey];
    [sourceOverCompositingFilter setValue:[[CIImage alloc] initWithImage:[UIImage imageNamed:@"background"]] forKey:kCIInputBackgroundImageKey];
    
    outputImage = sourceOverCompositingFilter.outputImage;
    CIContext  *context = [CIContext new];
    CGImageRef cgImage = [context createCGImage:outputImage fromRect:outputImage.extent];
    if (cgImage) {
        _iv.image = [UIImage imageWithCGImage:cgImage];
    }

方法2 像素点遍历

判断每一个像素点的颜色，如果在范围内修改点

- (UIImage *)removeWhiteColorWithImage:(UIImage *)image{
    return [self removeColorWithMaxR:255 minR:250 maxG:255 minG:250 maxB:255 minB:250 image:image];
}
- (UIImage *)removeColorWithMaxR:(float)maxR minR:(float)minR maxG:(float)maxG minG:(float)minG maxB:(float)maxB minB:(float)minB image:(UIImage *)image{
    // 分配内存
    const int imageWidth = image.size.width;
    const int imageHeight = image.size.height;
    size_t bytesPerRow = imageWidth * 4;
    uint32_t* rgbImageBuf = (uint32_t*)malloc(bytesPerRow * imageHeight);

    // 创建context
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();// 色彩范围的容器
    CGContextRef context = CGBitmapContextCreate(rgbImageBuf, imageWidth, imageHeight, 8, bytesPerRow, colorSpace,kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
    CGContextDrawImage(context, CGRectMake(0, 0, imageWidth, imageHeight), image.CGImage);


    // 遍历像素
    int pixelNum = imageWidth * imageHeight;
    uint32_t* pCurPtr = rgbImageBuf;
    for (int i = 0; i < pixelNum; i++, pCurPtr++)
    {
        uint8_t* ptr = (uint8_t*)pCurPtr;
        if (ptr[3] >= minR && ptr[3] <= maxR &&
            ptr[2] >= minG && ptr[2] <= maxG &&
            ptr[1] >= minB && ptr[1] <= maxB &&
            ptr[0] >0.5) {
            ptr[0] = 0;
            DBLog(@"白色变透明");
        }else{
            printf("\n---->ptr0:%d ptr1:%d ptr2:%d ptr3:%d<----\n",ptr[0],ptr[1],ptr[2],ptr[3]);
        }
    }
    // 将内存转成image
    CGDataProviderRef dataProvider =CGDataProviderCreateWithData(NULL, rgbImageBuf, bytesPerRow * imageHeight, nil);
    CGImageRef imageRef = CGImageCreate(imageWidth, imageHeight,8, 32, bytesPerRow, colorSpace,kCGImageAlphaLast |kCGBitmapByteOrder32Little, dataProvider,NULL,true,kCGRenderingIntentDefault);
    CGDataProviderRelease(dataProvider);
    UIImage* resultUIImage = [UIImage imageWithCGImage:imageRef];

    // 释放
    CGImageRelease(imageRef);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    return resultUIImage;
}

方法3 CGImageCreateWithMaskingColors

Creates a bitmap image by masking an existing bitmap image with the provided color values. 要掩盖的颜色值

 +(UIImage *(^)(UIImage *img))TransparentBackgroundImg{
    return ^UIImage *(UIImage *img){
         //    const float colorMasking[6] = {minR, maxR,  minG, maxG, minB, maxB};
         const CGFloat colorMasking[6] = {250.0, 255.0, 250.0, 255.0, 250.0, 255.0};
         CGImageRef sourceImage = img.CGImage;
          CGImageAlphaInfo info = CGImageGetAlphaInfo(sourceImage);
         if (info != kCGImageAlphaNone) {
             NSData *buffer = UIImageJPEGRepresentation(img, 1);
             UIImage *newImage = [UIImage imageWithData:buffer];
             sourceImage = newImage.CGImage;
         }
         
         CGImageRef masked = CGImageCreateWithMaskingColors(sourceImage, colorMasking);
         UIImage *retImage = [UIImage imageWithCGImage:masked];
         CGImageRelease(masked);
         return retImage;
         
        };
    
}

调用的时候直接调用：

[self.bankImg sd_setImageWithURL:urlStr(bill.organizationImg) completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                image = UoFactoryTool.TransparentBackgroundImg(image);
                //image = [self removeWhiteColorWithImage:image];
                image = [image imageWithRenderingMode: UIImageRenderingModeAlwaysTemplate];
                self.bankImg.image = image;
                self.bankImg.tintColor = [UIColor colorWithHexString:@"D8DADE"];
                
                
            }];

方法4 找设计师，简单性价比高

Graph Cut Grab Cut 待尝试