Meziantou.Framework.Imaging.Barcodes 1.0.0

Meziantou.Framework.Imaging.Barcodes

Renders the QR codes and barcodes of Meziantou.Framework.Barcodes as Meziantou.Framework.Imaging images. The resulting Image<Rgba32> can be saved in any format the library supports (PNG, WebP, JPEG, GIF, AVIF, ...), resized, or drawn onto another image.

Meziantou.Framework.Barcodes already writes PNG files on its own (ToPng), with no dependency. Use this package when you need another format or want to process the image further.

Usage

The types are in the Meziantou.Framework.Imaging.Barcodes namespace. The examples also use the Meziantou.Framework.Barcodes (QR codes and barcodes), Meziantou.Framework.Imaging (images) and Meziantou.Framework.Imaging.Formats (encoders) namespaces.

var qrCode = QRCode.Create("https://www.meziantou.net", ErrorCorrectionLevel.M);

// Default options: 10 pixels per module, a 4-module quiet zone, black on white
using var image = qrCode.ToImage();
Assert.Equal((330, 330), (image.Width, image.Height));

// Save to a file (image.Save("qrcode.webp", new WebPEncoder())) or to a stream
using var webp = new MemoryStream();
image.Save(webp, new WebPEncoder());

// Custom options, the same as the canvas drawing takes: any brush, and no background
using var customImage = qrCode.ToImage(new QRCodeDrawingOptions
{
    ModuleSize = 4,
    QuietZoneModules = 2,
    DarkBrush = new SolidBrush(new Rgba32(0x00, 0x33, 0x66)),
    LightBrush = null,
});
Assert.Equal((116, 116), (customImage.Width, customImage.Height));
Assert.Equal(Colors.Transparent, customImage.Frames[0][0, 0]);
Assert.Equal(new Rgba32(0x00, 0x33, 0x66), customImage.Frames[0][8, 8]);

// An indexed PNG stores the two colors in a palette, as ToPng does
using var png = new MemoryStream();
customImage.Save(png, new PngEncoder { PixelLayout = PngPixelLayout.Indexed });

Barcodes work the same way:

var barcode = Barcode.CreateEan13("5901234123457");
using var image = barcode.ToImage(new BarcodeDrawingOptions { ModuleWidth = 3, ModuleHeight = 100 });
Assert.Equal((345, 100), (image.Width, image.Height));

Drawing on a canvas

DrawQRCode and DrawBarcode draw on the DrawingCanvas of Image.Draw, as vector shapes: the transform, the clip and the layers of the canvas apply, and any Brush (solid, gradient, image, pattern) paints the modules. MeasureQRCode and MeasureBarcode give the size of the drawing beforehand, to lay out the page. With SnapToPixels (the default), the module sizes and the position are rounded to whole pixels, so that every module has the same size and sharp edges.

using var ticket = new Image<Rgba32>(400, 200, Colors.White); // or Image.Load<Rgba32>("ticket.png")
var qrCode = QRCode.Create("TICKET-0042");
var options = new QRCodeDrawingOptions { ModuleSize = 4, QuietZoneModules = 2 };

// The size of the drawing, quiet zone included, to lay out the page before drawing
var size = QRCodeImageRenderer.MeasureQRCode(qrCode, options);
Assert.Equal((100, 100), (size.Width, size.Height)); // (21 modules + 2 x 2) x 4 pixels

// Drawn as a vector shape: the transform and the clip of the canvas apply, any brush works
ticket.Draw(canvas => canvas.DrawQRCode(qrCode, new PointD(400 - 16 - size.Width, 16), options));
Assert.Equal(Colors.Black, ticket.Frames[0][284 + 8, 16 + 8]); // the top-left finder pattern, after the 8-pixel quiet zone

// Save to a file (ticket.Save("ticket-with-qrcode.png")) or to a stream
using var png = new MemoryStream();
ticket.Save(png, new PngEncoder());

DrawBarcode draws the bars, and the human-readable text (Barcode.Text, with its check digit) under them when BarcodeDrawingOptions.Font is set, for example to the bundled OCR-B font:

var barcode = Barcode.CreateEan13("590123412345");
var options = new BarcodeDrawingOptions
{
    ModuleWidth = 2,
    ModuleHeight = 60,
    QuietZoneModules = 9,
    DarkBrush = new SolidBrush(new Rgba32(0x00, 0x33, 0x66)),
    Font = BarcodeFonts.OcrB, // prints barcode.Text, "5901234123457", under the bars
    FontSize = 24,
};

var size = BarcodeImageRenderer.MeasureBarcode(barcode, options);
Assert.Equal(226, size.Width); // (95 modules + 2 x 9) x 2 pixels

using var label = new Image<Rgba32>(300, 140, Colors.White);
label.Draw(canvas => canvas.DrawBarcode(barcode, new PointD(20, 20), options));
Assert.Equal(new Rgba32(0x00, 0x33, 0x66), label.Frames[0][20 + 18, 50]); // the first guard bar

Fonts

BarcodeFonts.OcrA and BarcodeFonts.OcrB are the two fonts of optical character recognition, the ones usually printed under barcodes (OCR-B under EAN and UPC). They are generated from the character shapes of the standards, at their Size I and with their nominal stroke width, by tools/Meziantou.Framework.Imaging.Barcodes.FontGenerator:

• OCR-A from the dimensioned drawings of ANSI X3.17-1981: the centerlines in fractions of the character height and width, painted with a round pen, with the sharp corners the drawings show. The 2 degree lean of the stems of some small letters is not reproduced.
• OCR-B from the 4:1 illustrations of ANSI X3.49-1975 (the American counterpart of ECMA-11 and ISO 1073-2): the centerlines are traced from the illustrations, so they follow them within a few hundredths of a millimeter.

Both are monospaced (an advance of 0.6 em, the 0.1 inch pitch of the standards), map the printable ASCII characters, and are licensed with this package. OCR-A also maps the Hook, Chair and Fork (U+2440 to U+2442), which stand for the Tilde, the Grave Accent and the Underline; OCR-B also maps the letters of its extended repertoire (Ä, Å, Æ, Ö, Ø, Ü, Ñ, IJ, å, æ, ø, ij, ß) and §, ¤, £, ¥, ¨ and ´. The preferred shapes of the punctuation are drawn, not the alternate ones.

Options

ToImage and the canvas drawing take the same options: ToImage renders the drawing on an image of its size.