在iOS中使用CGImageRef和CGContextRef时增加内存

Question

每当这个方法调用它时，它会增加内存的大小。如何阻止内存大小的增加？

static unsigned char *RequestImagePixelData(UIImage *inImage) 
{
    CGImageRef img = [inImage CGImage]; 
    CGSize size = [inImage size];
    CGContextRef cgctx = CreateRGBABitmapContext(img); 
    CGRect rect = {{0,0},{size.width, size.height}};
    CGContextDrawImage(cgctx, rect, img);
    unsigned char *data = CGBitmapContextGetData (cgctx);
    CGContextRelease(cgctx);
    return data;
}