Piping ppm image to eog image viewer not working

问题

I am working on an image processing project in C++. To display the images I want to use the default ubuntu image viewer (eog). I have functions in my Image16 class which can read and write PPM files. I know these work because I can write them to the hard disk and then open them with eog. However I do not want to be writing the images to my hard disk because I have an SSD and each image is about 100 Mb. I want to directly pipe the image data into eog. This however is generating an error and I am not sure why.

ifstream in("/home/chase/Desktop/moon.ppm");
Image16 img = Image16::read_ppm(in);
in.close();

FILE* f = popen("eog /dev/stdin", "w");
img.write_ppm(f, 255);
pclose(f);