Hi, i wan to create an android application that uses camera and apply
some image processing filters of mine in real time. I have read from
the forums that Camera.PreviewCallback method onPreviewFrame has only
a copy of image data and if i alter them it has no effect (i 've seen
that after some time of work) . So i want to know if there is anyway
that i have not found that i can process the real frames. Another
approach that i try is to hide the camera preview surface and draw the
frames onto another surface but i cant hide the surface. I have read
from the forums (an this one) that if i do not use the
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); on the
usrfaceHolder then the surface view will be invisible but when i
remove this line of code or put SURFACE_TYPE_NURMAL as parameter my
application crashes. I have used only the emulator and i have not
tested it in my phone (galaxy s). My code is based on the code of
Google . If you can tell me what i do wrong or you can provide with
some code snippets that i can filter the frames it will be great help
because i have spent over 30hours on google search for that and still
no result
public class CameraPreview extends ViewGroup implements
SurfaceHolder.Callback, Camera.PreviewCallback {
private final String TAG = "Preview";
SurfaceView mSurfaceView;
SurfaceHolder mHolder;
Size mPreviewSize;
List<Size> mSupportedPreviewSizes;
Camera mCamera;
public CameraPreview(Context context) {
super(context);
mSurfaceView = new SurfaceView(context);
addView(mSurfaceView);
// Install a SurfaceHolder.Callback so we get notified when
the
// underlying surface is created and destroyed.
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_NORMAL);
//mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
//mHolder.setType(SurfaceHolder.SURFACE_TYPE_GPU);
}
public void setCamera(Camera camera) {
mCamera = camera;
if (mCamera != null) {
mSupportedPreviewSizes =
mCamera.getParameters().getSupportedPreviewSizes();
requestLayout();
}
}
public void switchCamera(Camera camera) {
setCamera(camera);
try {
camera.setPreviewDisplay(mHolder);
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()",
exception);
}
Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewSize(mPreviewSize.width,
mPreviewSize.height);
requestLayout();
camera.setParameters(parameters);
}
@Override
protected void onMeasure(int widthMeasureSpec, int
heightMeasureSpec) {
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview
instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(),
widthMeasureSpec);
final int height = resolveSize(getSuggestedMinimumHeight(),
heightMeasureSpec);
setMeasuredDimension(width, height);
if (mSupportedPreviewSizes != null) {
mPreviewSize =
getOptimalPreviewSize(mSupportedPreviewSizes, width, height);
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int
b) {
if (changed && getChildCount() > 0) {
final View child = getChildAt(0);
final int width = r - l;
final int height = b - t;
int previewWidth = width;
int previewHeight = height;
if (mPreviewSize != null) {
previewWidth = mPreviewSize.width;
previewHeight = mPreviewSize.height;
}
// Center the child SurfaceView within the parent.
if (width * previewHeight > height * previewWidth) {
final int scaledChildWidth = previewWidth * height /
previewHeight;
child.layout((width - scaledChildWidth) / 2, 0,
(width + scaledChildWidth) / 2, height);
} else {
final int scaledChildHeight = previewHeight * width /
previewWidth;
child.layout(0, (height - scaledChildHeight) / 2,
width, (height + scaledChildHeight) / 2);
}
}
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, acquire the camera and tell
it where
// to draw.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
}
} catch (IOException exception) {
Log.e(TAG, "IOException caused by setPreviewDisplay()",
exception);
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// Surface will be destroyed when we return, so stop the
preview.
if (mCamera != null) {
mCamera.stopPreview();
}
}
private Size getOptimalPreviewSize(List<Size> sizes, int w, int h)
{
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) w / h;
if (sizes == null) return null;
Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
// Try to find an size match aspect ratio and size
for (Size size : sizes) {
double ratio = (double) size.width / size.height;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE)
continue;
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
// Cannot find the one match the aspect ratio, ignore the
requirement
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
public void surfaceChanged(SurfaceHolder holder, int format, int
w, int h) {
// Now that the size is known, set up the camera parameters
and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setPreviewSize(mPreviewSize.width,
mPreviewSize.height);
requestLayout();
mCamera.setParameters(parameters);
mCamera.startPreview();
}
public void onPreviewFrame(byte[] data, Camera cam) {
//throw new UnsupportedOperationException("Not supported
yet.");
}
}
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