png_get_text() returns the text chunk information from the PNG stream in the array pointed to by text_ptr. It also returns the number of text chunks in num_text. text_ptr is an array of structure png_text whose members include:
type of compression used on text. Valid values are:
keyword for comment. Must contain 1-79 characters.
text comment for current keyword. May be empty.
length of text string after decompression. 0 for iTXt.