The AlphaBitmap created, or nil if the creation failed

The only file format currently supported is the PNG (Portable Network Graphics).
This format handles several functionalities, using blocks of information within the file.
In order to keep the library as light as possible, it was decided not to process some of these blocks, and therefore some information is not available. This does not mean that an image containing this information could not be displayed but simply that the information contained within these blocks would not be taken into account in displaying the image.

The following lists specify, in brackets, the names of these blocks as indicated in specification PNG 1.1.

Information supported :
- background color (bKGD)
- transparency (tRNS)

Information not supported :
- chromatic corrections (cHRM)
- gamma corrections (gAMA)
- pallet histogram (hIST)
- International Color Consortium profile (iCCP)
- actual pixel size and aspect ratio (pHYS)
- number of data bits (sBIT)
- suggested limited pallet (sPLT)
- International Color Consortium RGB color space (sRGB)
- text information (tEXt)
- date of last modification (tIME)
- zipped text information (zTXt)

Most existing decoders process these information blocks in a very random way. For example, aspect ratios are not taken into account by Photoshop or ACDSee while gamma corrections are handled (very poorly) by ACDSee but not by Photoshop.