A book is not always limited to text only, but can also contain illustrations (photos, drawings). Some books contain also figures, graphs, maps, etc. Such additional material may become blurry in e-books: on a small e-reader screen with bad resolution, minor details may disappear and their text part become unreadable. Unfortunately, most reading software programs do not enable enlarging the additional material contained in text. Besides, most images or pictures are in a raster format which makes an image or a picture unfocused after the enlargement.
The aforementioned problems are caused by the underpinning technology of e-books and there is no ideal solution to this.
If you create your book, keeping in mind from the very beginning the restrictions applied to an e-book, it is possible to achieve an appropriate result that works anywhere. The above-mentioned risks persist, if a work that was published at first as a printed matter is converted into e-book format. Therefore, it may happen that on some figures the most essential lines have become invisible.
We offer You some possibilities for improving the visibility of your figures.
You should avoid using very thin lines.
You should also avoid using very aeriform and decorative type of fonts.
If possible, please avoid crossing lines.
Do not place too much information on a figure.
Keep in mind that an average width of a figure is 9 cm on the screen.
Good results can also be achieved by referring to external sources. In other words, images or pictures that are essential for the content should be published on the internet on the homepage of a respective book, either in PDF or SVG format. In such case, links to these sources should be added to the e-book.