Adding read-image folder

[verma-ananya]

Following offline discussion with @krshrimali, we want to find a way to remove OpenCV dependency from the project. This will enable users to not require building OpenCV from source, which can create issues (see: https://github.com/opencv/opencv/issues?q=is%3Aopen+is%3Aissue+label%3A%22category%3A+build%2Finstall%22).

This PR attempts to start discussion on this topic. The first attempt is to compare using stb libraries for reading an image and resizing. Including the header files will be easier, and it will avoid the requirement to build the whole library (like OpenCV). This saves time, efforts but performance metric needs to be looked after.

Currently, this PR contains:

1. Sample codes for reading an image file using the STB library (independent of image format). [Code is in both C and C++]
2. Contains STB header files.

cc: @krshrimali

[krshrimali]

Thank you for your work, @verma-ananya. I left some minor comments. It will be great if we can:

• Add an example to resize an image using stb_image_resize library.
• Add self explanatory comments in the code, to allow future changes.
• Compare performance of OpenCV imread with stbi_load function.

Also, looking at the basic usage of stbi_load from https://github.com/nothings/stb/blob/master/stb_image.h#L124:

// Basic usage:
//    int x,y,n;
//    unsigned char *data = stbi_load(filename, &x, &y, &n, 0);
//    // ... process data if not NULL ...
//    // ... x = width, y = height, n = # 8-bit components per pixel ...
//    // ... replace '0' with '1'..'4' to force that many components per pixel
//    // ... but 'n' will always be the number that it would have been if you said 0
//    stbi_image_free(data)

From what I understand, the fourth argument is number of channels in the input image, and fifth argument is the output number of channels that we want in our image (I may be wrong). If this is true, then does it also mean that the user needs to know the number of channels in their dataset while using stbi_load function?

[krshrimali]

Is there any note on why this definition is needed?

[krshrimali]

Is this (image.cpp~) a possible duplicate of image.cpp file?

[krshrimali]

Closing this PR as this has been taken over by myself. I'll experiment using Selene! (https://github.com/kmhofmann/selene)