Create README.md

README.md

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+# About
+The framebuffer library was created to have an easy way to access the pixels on the screen from the Raspberry Pi.
+It memory-maps the framebuffer device and provides it as a draw.Image (which is itself an image.Image).
+This makes it easy to use with Go's image, color and draw packages.
+
+Right now the library only implements the RGB 565 color model, which is the default under Raspbian. Also the OS is assumed to be
+little endian, also the default for Raspbian.
+
+# Usage
+To access the framebuffer you have to call Open and pass the device file to it. When you are done, call Close on the returned device.
+Note that you usually need root access for this so make sure to run your program as a super user.
+
+Once you have a device open you can use it like a Go draw.Image (image.Image).
+
+Here is a simple example that clears the whole screen to a dark magenta:
+
+```Go
+package main
+
+import (
+	"github.com/gonutz/framebuffer"
+	"image"
+	"image/color"
+	"image/draw"
+)
+
+func main() {
+	fb, err := framebuffer.Open("/dev/fb0")
+	if err != nil {
+		panic(err)
+	}
+	defer fb.Close()
+
+	magenta := image.NewUniform(color.RGBA{255, 0, 128, 255})
+	draw.Draw(fb, fb.Bounds(), magenta, image.ZP, draw.Src)
+}
+```