Add image I/O unit tests

[dictoon]

Generate then write a test image, read it back, compare.

Test a variety of formats (PNG, JPEG, BMP, TIFF, OpenEXR).

[ChinYing-Li]

I am Alice, and would be great if you can assign me this issue. I just added my test_imagewriter.cpp file to the build.

[oktomus]

I am Alice, and would be great if you can assign me this issue. I just added my test_imagewriter.cpp file to the build.

No need to assign issues @ChinYing-Li, you can just start working on it :)

[dictoon]

Actually it's a good practice to assign issues, it's just that sometimes we're lazy :)

[Abhinavcode13]

Is this problem resolved? If not, could you please assign it to me?