来源： Android OpenGL Camera Preview Issue
‘m working on an Android camera app that modifies the camera feed and displays it live on the screen. I have it working and doing what I want perfectly on my DROID RAZR MAXX running 4.3, and it works perfect on other phones, but unfortunately I have ran into a problem on several phones and am unable to track down the issue.
I’ve attached a screenshot showing what the issue is.
It’s very hard to tell what the green “artifacts” are, but it almost looks like it’s blocks from the camera feed from when it first turned on. The colors flicker, but the shapes inside the blocks don’t really change.
I’ve stripped out everything that isn’t needed and cleaned up the code as best I can, but I honestly have zero clue as to why this is happening, especially since it seems to work on some phones fine, while other phones it doesn’t.
If I need to give more information just comment and I will add it!
CameraActivity.java
<pre><code>public class CameraActivity extends Activity
{
private MyGLSurfaceView glSurfaceView;
private MyCamera mCamera;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
mCamera = new MyCamera();
glSurfaceView = new MyGLSurfaceView(this, mCamera);
setContentView(glSurfaceView);
}
@Override
protected void onPause()
{
super.onPause();
mCamera.stop();
}
}
MyCamera.java
<pre><code>public class MyCamera
{
private final static String LOG_TAG = "MyCamera";
private Camera mCamera;
private Parameters mCameraParams;
private Boolean running = false;
void start(SurfaceTexture surface)
{
Log.v(LOG_TAG, "Starting Camera");
mCamera = Camera.open(0);
mCameraParams = mCamera.getParameters();
Log.v(LOG_TAG, mCameraParams.getPreviewSize().width + " x " + mCameraParams.getPreviewSize().height);
try {
mCamera.setPreviewTexture(surface);
mCamera.startPreview();
running = true;
} catch (IOException e) {
e.printStackTrace();
}
}
void stop()
{
if (running) {
Log.v(LOG_TAG, "Stopping Camera");
mCamera.stopPreview();
mCamera.release();
running = false;
}
}
}
MyGLSurfaceView.java
<pre><code>class MyGLSurfaceView extends GLSurfaceView implements Renderer
{
private final static String LOG_TAG = "MyGLSurfaceView";
private MyCamera mCamera;
private SurfaceTexture mSurface;
private DirectVideo mDirectVideo;
public MyGLSurfaceView(Context context, MyCamera camera)
{
super(context);
mCamera = camera;
setEGLContextClientVersion(2);
setRenderer(this);
}
@Override
public void onDrawFrame(GL10 gl)
{
float[] mtx = new float[16];
mSurface.updateTexImage();
mSurface.getTransformMatrix(mtx);
mDirectVideo.draw();
}
@Override
public void onSurfaceChanged(GL10 gl, int width, int height)
{
Log.v(LOG_TAG, "Surface Changed");
GLES20.glViewport(0, 0, width, height);
}
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config)
{
Log.v(LOG_TAG, "Surface Created");
int texture = createTexture();
mDirectVideo = new DirectVideo(texture);
mSurface = new SurfaceTexture(texture);
mCamera.start(mSurface);
}
private int createTexture()
{
int[] textures = new int[1];
// generate one texture pointer and bind it as an external texture.
GLES20.glGenTextures(1, textures, 0);
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textures[0]);
// No mip-mapping with camera source.
GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
// Clamp to edge is only option.
GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE);
GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE);
return textures[0];
}
public static int loadShader(int type, String shaderCode){
// create a vertex shader type (GLES20.GL_VERTEX_SHADER)
// or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
int shader = GLES20.glCreateShader(type);
// add the source code to the shader and compile it
GLES20.glShaderSource(shader, shaderCode);
GLES20.glCompileShader(shader);
return shader;
}
}
DirectVideo.java
<pre><code>public class DirectVideo
{
private final String vertexShaderCode =
"attribute vec4 vPosition;" +
"attribute vec2 inputTextureCoordinate;" +
"varying vec2 textureCoordinate;" +
"void main()" +
"{"+
"gl_Position = vPosition;"+
"textureCoordinate = inputTextureCoordinate;" +
"}";
private final String fragmentShaderCode =
"#extension GL_OES_EGL_image_external : require\n"+
"precision mediump float;" +
"varying vec2 textureCoordinate;\n" +
"uniform samplerExternalOES s_texture;\n" +
"void main() {" +
" gl_FragColor = texture2D( s_texture, textureCoordinate );\n" +
"}";
private FloatBuffer vertexBuffer, textureVerticesBuffer;
private ShortBuffer drawListBuffer;
private final int mProgram;
private int mPositionHandle;
private int mTextureCoordHandle;
private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices
// number of coordinates per vertex in this array
private static final int COORDS_PER_VERTEX = 2;
private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
static float squareCoords[] = {
-1.0f, 1.0f,
-1.0f, -1.0f,
1.0f, -1.0f,
1.0f, 1.0f,
};
static float textureVertices[] = {
0.0f, 1.0f,
1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 0.0f,
};
private int texture;
public DirectVideo(int texture)
{
this.texture = texture;
// initialize vertex byte buffer for shape coordinates
ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4);
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(squareCoords);
vertexBuffer.position(0);
// initialize byte buffer for the draw list
ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2);
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
ByteBuffer bb2 = ByteBuffer.allocateDirect(textureVertices.length * 4);
bb2.order(ByteOrder.nativeOrder());
textureVerticesBuffer = bb2.asFloatBuffer();
textureVerticesBuffer.put(textureVertices);
textureVerticesBuffer.position(0);
int vertexShader = MyGLSurfaceView.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = MyGLSurfaceView.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
mProgram = GLES20.glCreateProgram(); // create empty OpenGL ES Program
GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program
GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
GLES20.glLinkProgram(mProgram); // creates OpenGL ES program executables
}
public void draw()
{
GLES20.glUseProgram(mProgram);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture);
// get handle to vertex shader's vPosition member
mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
// Enable a handle to the triangle vertices
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Prepare the <insert shape here> coordinate data
GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);
mTextureCoordHandle = GLES20.glGetAttribLocation(mProgram, "inputTextureCoordinate");
GLES20.glEnableVertexAttribArray(mTextureCoordHandle);
GLES20.glVertexAttribPointer(mTextureCoordHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, textureVerticesBuffer);
GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer);
// Disable vertex array
GLES20.glDisableVertexAttribArray(mPositionHandle);
GLES20.glDisableVertexAttribArray(mTextureCoordHandle);
}
}
In the onDrawFrame method you get a transformation matrix, but you don’t use it. This matrix should be used to transform texture coordinates. For details see the documentation of the SurfaceTexture class.
Here is the fix:
- pass the matrix to the the draw method:
@Override
public void onDrawFrame(GL10 gl)
{
float[] mtx = new float[16];
mSurface.updateTexImage();
mSurface.getTransformMatrix(mtx);
mDirectVideo.draw(mtx);
}
- Add the following method to the DirectVideo class:
private float[] transformTextureCoordinates( float[] coords, float[] matrix)
{
float[] result = new float[ coords.length ];
float[] vt = new float[4];
for ( int i = 0 ; i < coords.length ; i += 2 ) {
float[] v = { coords[i], coords[i+1], 0 , 1 };
Matrix.multiplyMV(vt, 0, matrix, 0, v, 0);
result[i] = vt[0];
result[i+1] = vt[1];
}
return result;
}
- In the draw method Convert the textureVertices list before adding to the buffer ( you should do this conversion at every paint since the matrix can change):
textureVerticesBuffer.clear();
textureVerticesBuffer.put( transformTextureCoordinates( textureVertices, mtx ));
textureVerticesBuffer.position(0);
An alternative solution is if you pass the matrix to the shader.
Mikel
