Block iteration
The TIFF format is a versatile image format that can be customized for very diverse needs. The file is composed of a Header, at least one Image File Directory, and any amount of Image Data. Explaining it in a simple way, the header tells where the first directory is on the file. The directory contains information about the image, tells how to read the data related to it, and tells where the next directory is. Each combination of a directory and image data is an image, so a single TIFF file may have multiple images inside it.
Each image data (a whole image) contains blocks of data (that is, parts of the image) that can be read separately, each one representing a specific region of the image. This allows the user to read the image by chunks, just like we did.
The blocks of data are indivisible; in order to return data from an image, the program that is reading it needs to read at least one whole block. If the desired region is smaller than a block, the whole block will be read...
