我想在屏幕上显示2个视图 – 一个是相机预览,在顶部,而另一个将显示图像或谷歌地图 – 并且生活在屏幕的底部.
我想要在它们之间有一个梯度的过渡 – 所以它们之间没有粗略的界限.有可能有这样的效果吗？
编辑：
我想要实现的效果应该是这样(顶部来自相机预览,而底部应该是一个地图…)：
在iOS上,与CameraOverlay类似的效果显示地图,并将层masp设置为渐变：
CAGradientLayer *gradient = [CAGradientLayer layer]; gradient.frame = self.map.bounds; gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithWhite: 1.0 alpha: 0.0] CGColor],(id)[[UIColor colorWithWhite: 1.0 alpha: 1.0] CGColor],nil]; gradient.startPoint = CGPointMake(0.5f,0.0f); gradient.endPoint = CGPointMake(0.5f,0.5f); self.map.layer.mask = gradient;
解决方法
这可能,但也许有点复杂.为了保持简单,我已经将核心代码放在了解中.如前所述,您需要两个观点来做到这一点,一个是“另一个”. “lower”应该是由Maps API驱动的SurfaceView. “较高”的应该显示相机图像在其上淡出.
编辑：正如mr_archano指出的那样,API(现在)被定义为没有SurfaceView,摄像头就不会发送预览数据.哼哼,这是进步的本质,但是这也是最重要的.
>“下”SurfaceView由摄像机预览机制直接驱动.
>“中间”SurfaceView是针对MAPS API的.
>“上”视图是摄像机数据呈现以达到预期效果的位置.
核心代码因此在“相机预览”上提供“相机预览”,并且上部图片被有意地扭曲,因此它在顶部完全清晰可见,在中间淡出并且在底部.
我可以建议使用这个代码的最好方法是自己实现这四个步骤,看看它的工作,然后添加两个最后的步骤,看看工作,然后将关键概念插入另一个,无疑是更大更多复杂的代码片段.
前四步：
>创建自定义视图以显示到顶部,相机,视图.这个类对它下面的任何内容都进行了一个位图.位图中每个像素中的alpha值将决定下图中多少通过.
public class CameraOverlayView extends View {
private Paint paint;
private Size incomingSize;
private Bitmap bitmap = null;
public CameraOverlayView(Context context) {
super(context);
init();
}
public CameraOverlayView(Context context,AttributeSet attrs) {
super(context,attrs);
init();
}
private void init() {
paint = new Paint();
paint.setStyle(Style.FILL_AND_STROKE);
paint.setColor(0xffffffff);
paint.setTextSize((float) 20.0);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
int width = canvas.getWidth();
int height = canvas.getHeight();
canvas.drawBitmap(bitmap,0.0f,paint);
}
}
>将三个视图放在一个框架中,它们都在两个方向都设置为ff_p_parent.第一个将是“下面”(SurfaceView,因此相机预览可以工作).第二个“中间”(地图或任何地图的视图).第三个“顶部”(褪色的相机图像的视图).
<SurfaceView
android:id="@+id/beneathSurfaceView"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<SurfaceView
android:id="@+id/middleSurfaceView"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<com.blah.blah.blah.CameraOverlayView
android:id="@+id/aboveCameraView"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
>删除主要Activity将设置相机,并将自动预览图像发送到(底部)SurfaceView和预览图像数据到处理例程.它设置一个回调来捕获预览数据.这两个并行运行.
public class CameraOverlay extends Activity implements SurfaceHolder.Callback2 {
private SurfaceView backSV;
private CameraOverlayView cameraV;
private SurfaceHolder cameraH;
private Camera camera=null;
private Camera.PreviewCallback cameraCPCB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.camera_overlay);
// Get the two views
backSV = (SurfaceView) findViewById(R.id.beneathSurfaceView);
cameraV = (CameraOverlayView) findViewById(R.id.aboveCameraView);
// BACK: Putting the camera on the back SV (replace with whatever is driving that SV)
cameraH = backSV.getHolder();
cameraH.addCallback(this);
// FRONT: For getting the data from the camera (for the front view)
cameraCPCB = new Camera.PreviewCallback () {
@Override
public void onPreviewFrame(byte[] data,Camera camera) {
cameraV.acceptCameraData(data,camera);
}
};
}
// Making the camera run and stop with state changes
@Override
public void onResume() {
super.onResume();
camera = Camera.open();
camera.startPreview();
}
@Override
public void onPause() {
super.onPause();
camera.setPreviewCallback(null);
camera.stopPreview();
camera.release();
camera=null;
}
private void cameraImageToViewOn() {
// FRONT
cameraV.setIncomingSize(camera.getParameters().getPreviewSize());
camera.setPreviewCallback(cameraCPCB);
}
private void cameraImageToViewOff() {
// FRONT
camera.setPreviewCallback(null);
}
// The callbacks which mean that the Camera does stuff ...
@Override
public void surfaceChanged(SurfaceHolder holder,int format,int width,int height) {
// If your preview can change or rotate,take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (holder == null) return;
// stop preview before making changes
try {
cameraImageToViewOff(); // FRONT
camera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize,rotate or reformatting changes here
// start preview with new settings
try {
camera.setPreviewDisplay(holder); //BACK
camera.startPreview();
cameraImageToViewOn(); // FRONT
} catch (Exception e){
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
camera.setPreviewDisplay(holder); //BACK
camera.startPreview();
cameraImageToViewOn(); // FRONT
} catch (IOException e) {
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
@Override
public void surfaceRedrawNeeded(SurfaceHolder holder) {
}
}
有些事情缺少：
确保相机图像是正确的方向
>确保相机预览图像是最佳尺寸
>现在,在第一步中创建的视图中添加两个函数.第一个确保视图知道传入的图像数据的大小.第二个接收预览图像数据,将其转换为位图,使其沿着可见性扭曲,并显示Alpha渐变.
public void setIncomingSize(Size size) {
incomingSize = size;
if (bitmap != null) bitmap.recycle();
bitmap = Bitmap.createBitmap(size.width,size.height,Bitmap.Config.ARGB_8888);
}
public void acceptCameraData(byte[] data,Camera camera) {
int width = incomingSize.width;
int height = incomingSize.height;
// the bitmap we want to fill with the image
int numPixels = width*height;
// the buffer we fill up which we then fill the bitmap with
IntBuffer intBuffer = IntBuffer.allocate(width*height);
// If you're reusing a buffer,next line imperative to refill from the start,- if not good practice
intBuffer.position(0);
// Get each pixel,one at a time
int Y;
int xby2,yby2;
int R,G,B,alpha;
float U,V,Yf;
for (int y = 0; y < height; y++) {
// Set the transparency based on how far down the image we are:
if (y<200) alpha = 255; // This image only at the top
else if (y<455) alpha = 455-y; // Fade over the next 255 lines
else alpha = 0; // nothing after that
// For speed's sake,you should probably break out of this loop once alpha is zero ...
for (int x = 0; x < width; x++) {
// Get the Y value,stored in the first block of data
// The logical "AND 0xff" is needed to deal with the signed issue
Y = data[y*width + x] & 0xff;
// Get U and V values,stored after Y values,one per 2x2 block
// of pixels,interleaved. Prepare them as floats with correct range
// ready for calculation later.
xby2 = x/2;
yby2 = y/2;
U = (float)(data[numPixels + 2*xby2 + yby2*width] & 0xff) - 128.0f;
V = (float)(data[numPixels + 2*xby2 + 1 + yby2*width] & 0xff) - 128.0f;
// Do the YUV -> RGB conversion
Yf = 1.164f*((float)Y) - 16.0f;
R = (int)(Yf + 1.596f*V);
G = 2*(int)(Yf - 0.813f*V - 0.391f*U); // Distorted to show effect
B = (int)(Yf + 2.018f*U);
// Clip rgb values to 0-255
R = R < 0 ? 0 : R > 255 ? 255 : R;
G = G < 0 ? 0 : G > 255 ? 255 : G;
B = B < 0 ? 0 : B > 255 ? 255 : B;
// Put that pixel in the buffer
intBuffer.put(Color.argb(alpha,R,B));
}
}
// Get buffer ready to be read
intBuffer.flip();
// Push the pixel information from the buffer onto the bitmap.
bitmap.copyPixelsFromBuffer(intBuffer);
this.invalidate();
}
关于第二个例程的注意事项：
>它假设入射摄像机格式NV21.其他的可能是可以使用的,即使是痛苦也是有保证的.见Converting YUV->RGB(Image processing)->YUV during onPreviewFrame in android?.
>它可能会更快,更好,更新版本的Android和一些代码优化.
>将相机表面视图设置得足够小以隐藏在顶视图的非褪色部分之后.即,将android：layout_height更改为,例如60dp.>设置中间的SurfaceView接收地图信息.
