Textastic supports the preview function of iOS which allows you to view image, pdf and office files.
Tap and hold the file to display the width and height of image files in pixels (1024 x 768 in this case).
For binary files, Textastic automatically opens the preview screen when you tap on it.
For text files, you can tap and hold a file and select "Preview" to open the preview screen.
Use "Open with Encoding" to open the file using a specific character encoding. This is useful if Textastic cannot automatically detect the character encoding of a file.
Tap on "Open In..." to open the file in another app that can edit or view this type of file.
You can also use "Send as Attachment" to send any file as a mail attachment.