Later versions of the Android SDK seem to have this feature also but let's not forget that there are still a huge proportion of 2.3 phones out there that could be supported if only this was a simple feature.
Well, I brute-forced one that runs on OpenGL on a 2.3.3 phone.
#1 I created a camera preview listener and the associated classes to provide a nice .net event when the new camera frame arrived:
public class CameraListener
: Java.Lang.Object, Camera.IPreviewCallback
{
public event PreviewFrameHandler
PreviewFrame;
public void OnPreviewFrame(byte[]
data, Camera camera)
{
if
(PreviewFrame != null)
{
PreviewFrame(this, new PreviewFrameEventArgs(data, camera));
}
}
}
public delegate void PreviewFrameHandler(object
sender, PreviewFrameEventArgs e);
public class PreviewFrameEventArgs
: EventArgs
{
byte[]
_data;
Camera
_camera;
public byte[] Data { get { return _data; } }
public Camera Camera { get
{ return _camera; } }
public PreviewFrameEventArgs(byte[] data, Camera
camera)
{
_data = data;
_camera = camera;
}
}
#2 Using MonoGame I created a basic app
public class Game1 :
Microsoft.Xna.Framework.Game
{
Camera
_camera;
CameraListener
_listener = new CameraListener();
GraphicsDeviceManager
graphics;
SpriteBatch
spriteBatch;
SpriteFont
font;
Texture2D
_cameraBG;
short[]
_frameData = null;
public
Game1()
{
graphics = new
GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
graphics.IsFullScreen = true;
graphics.PreferredBackBufferWidth =
800;
graphics.PreferredBackBufferHeight
= 480;
graphics.SupportedOrientations = DisplayOrientation.LandscapeLeft | DisplayOrientation.LandscapeRight;
_listener.PreviewFrame += new PreviewFrameHandler(_listener_PreviewFrame);
}
unsafe void _listener_PreviewFrame(object
sender, PreviewFrameEventArgs e)
{
lock
(this)
{
fixed
(short* fd = &_frameData[0])
{
fixed
(byte* yuv = &e.Data[0])
{
YUV2RGB.convertYUV420_NV21toRGB5551(yuv, fd,
_cameraBG.Width, _cameraBG.Height);
}
}
_cameraBG.SetData(_frameData);
}
}
/// <summary>
/// Allows the game to perform any initialization it needs to
before starting to run.
/// This is where it can query for any required services and
load any non-graphic
/// related content.
Calling base.Initialize will enumerate through any components
/// and initialize them as well.
/// </summary>
protected
override void
Initialize()
{
// TODO: Add your initialization logic here
base.Initialize();
_camera = Camera.Open();
Camera.Parameters parameters = _camera.GetParameters();
IList<Camera.Size>
sizes = parameters.SupportedPreviewSizes;
_cameraBG = new Texture2D(graphics.GraphicsDevice,
sizes[9].Width, sizes[9].Height, false, SurfaceFormat.Bgra5551);
_frameData=new
short[sizes[9].Width*sizes[9].Height];
parameters.SetPreviewSize(sizes[9].Width, sizes[9].Height);
_camera.SetParameters(parameters);
_camera.SetPreviewCallback(_listener);
_camera.StartPreview();
}
/// <summary>
/// LoadContent will be called once per game and is the place
to load
/// all of your content.
/// </summary>
protected
override void
LoadContent()
{
// Create
a new SpriteBatch, which can be used to draw textures.
spriteBatch = new SpriteBatch(GraphicsDevice);
// TODO: use this.Content to load your game content here
font = Content.Load<SpriteFont>("spriteFont1");
}
/// <summary>
/// Allows the game to run logic such as updating the world,
/// checking for collisions, gathering input, and playing
audio.
/// </summary>
/// <param
name="gameTime">Provides a
snapshot of timing values.</param>
protected
override void
Update(GameTime gameTime)
{
if
(GamePad.GetState(PlayerIndex.One).Buttons.Back
== ButtonState.Pressed)
{
Exit();
}
// TODO: Add your update logic here
base.Update(gameTime);
}
int c =
0;
/// <summary>
/// This is called when the game should draw itself.
/// </summary>
/// <param
name="gameTime">Provides a
snapshot of timing values.</param>
protected
override void
Draw(GameTime gameTime)
{
graphics.GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
spriteBatch.Draw(_cameraBG, new Rectangle(0,0,graphics.GraphicsDevice.Viewport.Width,
graphics.GraphicsDevice.Viewport.Height), Color.White);
spriteBatch.DrawString(font, "Hello from MonoGame!", new Vector2(c++,
16), Color.White);
spriteBatch.End();
if
(c > 350)
c = 0;
base.Draw(gameTime);
}
#3 Using info gleaned from Wikipedia I put together a YUV to RGB translator NOTE the use of unsafe code. Sorry but that's the way it has to be.
public static class YUV2RGB
{
unsafe public static void convertYUV420_NV21toRGB4444(byte* yuvIn, short*
rgbOut , int width, int
height)
{
int
size = width * height;
int
offset = size;
int
u, v, y1, y2, y3, y4;
for
(int i = 0, k = 0; i < size; i += 2, k += 2)
{
y1 = yuvIn[i];
y2 = yuvIn[i + 1];
y3 = yuvIn[width + i];
y4 = yuvIn[width + i + 1];
u = yuvIn[offset + k];
v =
yuvIn[offset + k + 1];
u = u - 128;
v = v - 128;
convertYUVtoRGB4444(y1, u, v, rgbOut, i);
convertYUVtoRGB4444(y2, u, v, rgbOut, (i + 1));
convertYUVtoRGB4444(y3, u, v, rgbOut, (width + i));
convertYUVtoRGB4444(y4, u, v, rgbOut, (width + i + 1));
if (i != 0 && (i + 2) %
width == 0)
i += width;
}
}
unsafe private static void convertYUVtoRGB4444(int
y, int u, int
v, short* rgbOut, int
index)
{
int r = y + (int)1.402f * v;
int g = y - (int)(0.344f * u + 0.714f * v);
int b = y + (int)1.772f * u;
r = r > 255 ? 255 : r < 0 ? 0 : r;
g = g > 255 ? 255 : g < 0 ? 0 : g;
b = b > 255 ? 255 : b < 0 ? 0 : b;
rgbOut[index] = (short)(0xf000 | ((r&0xf0)<<8) |
((g&0x00f0)<<4) | b>>4);
}
unsafe public static void convertYUV420_NV21toRGB5551(byte* yuvIn, Int16*
rgbOut, int width, int
height)
{
int
size = width * height;
int
offset = size;
int
u, v, y1, y2, y3, y4;
for
(int i = 0, k = 0; i < size; i += 2, k += 2)
{
y1 = yuvIn[i];
y2 = yuvIn[i + 1];
y3 = yuvIn[width + i];
y4 = yuvIn[width + i + 1];
u = yuvIn[offset + k];
v = yuvIn[offset + k + 1];
u = u - 128;
v = v - 128;
convertYUVtoRGB5551(y1, u, v, rgbOut, i);
convertYUVtoRGB5551(y2, u, v, rgbOut, (i + 1));
convertYUVtoRGB5551(y3, u, v, rgbOut, (width + i));
convertYUVtoRGB5551(y4, u, v, rgbOut, (width + i + 1));
if (i != 0 && (i + 2) %
width == 0)
i += width;
}
}
unsafe private static void convertYUVtoRGB5551(int
y, int u, int
v, Int16* rgbOut, int
index)
{
int
r = y + (int)1.402f * v;
int
g = y - (int)(0.344f * u + 0.714f * v);
int
b = y + (int)1.772f * u;
r = r > 255 ? 255 : r < 0 ? 0
: r;
g = g > 255 ? 255 : g < 0 ? 0
: g;
b = b > 255 ? 255 : b < 0 ? 0
: b;
rgbOut[index]=(short)(((b&0xf8) << 8) |
((g&0xf8)
<< 3) |
((r >> 2) &
0x3e |
1)
);
}
}
