README.md

Writer

Writer folders contains built-in writers those implement qrcode.Writer:

// Writer is the interface of a QR code writer, it defines the rule of how to
// `print` the code image from matrix. There's built-in writer to output into
// file, terminal.
type Writer interface {
	// Write writes the code image into itself stream, such as io.Writer,
	// terminal output stream, and etc
	Write(mat matrix.Matrix) error
	
	// Close the writer stream if it exists after QRCode.Save() is called.
	Close() error
}

Implementations

• Standard output file writer
• Terminal output writer

How to customize your own writer?

As you can see, the writer is a simple interface, you can implement your own writer to fit your needs. The prerequisites are:

• Already understand Writer interface usage.
• Have understood about paint a picture with go (of course you can refer standard implementation).
• QR Code matrix is a 2D array of martix.State, we can simply divide these states into binary value (0/1), as the following table:

State Expr	value	representation
StateFalse	0	unset (data and etc)
ZERO	0	same as StateFalse
StateTrue	1	set (data)
StateInit	1	not changed since initialized (temporary state)
StateVersion	1	set (qr version)
StateFormat	1	set (qr format)
StateFinder	1	set (qr finder)

Now, you can implement your own writer to fit your needs, let's use pseudocode to discuss:

// define your own writer structure to implement `Writer` interface.
object writer {};

writer.Write(matrix.Matrix):
	// these should be `IMAGE` stream controller, it receives matrix
	// it decide how to print the image. 
	object paint;  
	
	// set use BLACK, unset use WHITE. Or provides matrix.State to colors mapping
	// so that you can control QR Image output intensively. 
	foreach row in matrix:
		foreach column in row:
			if column.State in [StateFalse]:
				// paint a WHITE square block
				paint.draw(x, y, WHITE);
			else:
				// paint a BLACK square block, 
				paint.draw(x, y, BLACK);
	// loop end;
	// output paint;