An easy to use library for interacting with the Linux framebuffer interface (/dev/fbX)
Get Started
$ dotnet add package Nfw.Linux.FrameBufferReadme
Nfw.Linux.FrameBuffer
An easy to use library for interacting with the Linux framebuffer interface (/dev/fbX).
NuGet
dotnet add package Nfw.Linux.FrameBuffer
Samples: Get Info From Display
This small snippet will open the provided device and use ioctls to discover its identifier and display parameters:
using(RawFrameBuffer fb = new RawFrameBuffer("/dev/fb0")) {
Console.WriteLine($"Display Device => {fb.Device} Name => {fb.Id} Width => {fb.PixelWidth} Height => {fb.PixelHeight} Bpp => {fb.PixelDepth}");
}
Samples: Write Pixels
This snippet shows how you can write raw pixel data (on a 16bpp screen this shows as Black and Red hatch):
using(RawFrameBuffer fb = new RawFrameBuffer("/dev/fb0")) {
// For each pixel, flop between 0x00 and 0x80
byte[] data = new byte[fb.PixelWidth * fb.PixelHeight * (fb.PixelDepth / 8)];
byte flopMe = 0x00;
for (int x = 0; x < data.Length; x += (fb.PixelDepth / 8)) {
for (int pixelByte = 0; pixelByte < (fb.PixelDepth / 8); pixelByte++) {
data[x + pixelByte] = flopMe;
}
flopMe = (flopMe == 0x00) ? (byte) 0x80 : (byte) 0x00;
}
fb.WriteRaw(data);
}
Samples: Displaying an Image
This snippet uses the fantastic ImageSharp library to load an image, which must be in the same bitdepth as the framebuffer, then write it to the framebuffer:
using(RawFrameBuffer fb = new RawFrameBuffer("/dev/fb0")) {
byte[] pixelBytes = new byte[fb.PixelWidth * fb.PixelHeight * (fb.PixelDepth / 8)];
// Load from source
using(Image loadedImage = Image.Load(filename)) {
// Resize to fit screen
loadedImage.Mutate(x => {
x.Resize(fb.PixelWidth, fb.PixelHeight);
});
// Write the raw pixel data into a buffer
loadedImage.CopyPixelDataTo(pixelBytes);
fb.WriteRaw(pixelBytes);
}
}
More useful is converting from whatever the image format is on disk, to the framebuffer's format, see the DisplayImage Sample - which uses ImageSharp AND convert the image to the same pixel format as the display before writing the pixel data itself to the framebuffer.
Notes
- The RawFrameBuffer constructor can optionally be told NOT to probe via ioctl on construction, instead post-construction you must call
RefreshDeviceInfo()before you can render anything. - The RawFrameBuffer constructor can also be optionally provided an
ILogger, perhaps via IoC, for logging/diagnostics. - In the case where your FB device can be mirrored, I suggest writing to the fastest (i.e. /dev/fb0 is often HW accelerated) then mirroring via something like the raspi2fb tool to effectively 'double buffer'.
References
Attribution
IMAGE LICENSE
The Sample Image used is an original watercolor by the author's wife: Katie Yocom. License for this file is CC BY-NC-ND 4.0.
Changelog
- 1.0.3:
- Blank() now defaults to FB_BLANK_NORMAL
- PowerDown() was added for previous behavior
- Also exposes a Blank(byte) which takes arbitrary ioctl value.