I have an app with a ViewSwitcher which holds a MapView and another View and I want to save the MapView's bitmap as an image. This works well, if the MapView has been visible at least once by doing something like that:
mapView.setDrawingCacheEnabled(true);
Bitmap bm = mapView.getDrawingCache();
/* ... save bitmap ... */
Problem is, if the MapView hasn't been visible, getDrawingCache() returns null for the bitmap. Is there any way how I can resolve that?
I found out how to do it. There are two things to do:
To get the bitmap, create your own one and make the MapView draw into it:
Bitmap bm = Bitmap.createBitmap(400, 400, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bm);
mapView.draw(canvas);
If you do so, you'll have all your overlays in the bitmap, but not the map image (the tiles). To achieve that too, you'll have to invoke mapView.preLoad() prior to drawing the map onto your bitmap.
Related
My program is a simple flood-fill game application for android, namely, the user can paint and draw something on the canvas. Now I want to provide a sharing option to the users. I guess that I must begin with copying the canvas to a bitmap object. I could not find a satisfactory answer because it is generally suggested "to create a new canvas, then..." but I got a canvas like that,
Canvas canvas = holder.lockCanvas();
then I use it. So, how can I copy my current canvas to a bitmap object?
Thanks
As suggested Maulik.J, I looked at converting a canvas into bitmap image in android again.
I could not understand from a bit close expression of this link. But, then I saw below text taken from http://developer.android.com/guide/topics/graphics/2d-graphics.html#draw-with-canvas . So, I solved this problem with the help of Maulik.J and the following text:
The Bitmap is always required for a Canvas. You can set up a new Canvas like this:
Bitmap b = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
Now your Canvas will draw onto the defined Bitmap. After drawing upon it with the Canvas, you can then carry your Bitmap to another Canvas with one of the Canvas.drawBitmap(Bitmap,...) methods. It's recommended that you ultimately draw your final graphics through a Canvas offered to you by View.onDraw() or SurfaceHolder.lockCanvas()
I created a second Canvas object having a bitmap which has same dimensions with my real canvas, I drew all my illustrations on this second temporary canvas. Then, I drew its bitmap on my real canvas.
Thanks.
I know - the title may sounds strange. Let me explain:
I created an image to show you, what I'm talking about:
I got an image (Bitmap (1)), that as the size of 150w/200h.
Now I need to make the bitmap bigger ((2) 400w/400h), but the original image must have the same size. So that the image is embedded in white background.
I think one way to solve it is this:
* create a big bitmap
* create a canvas for it
* draw the original bitmap on the canvas
* draw the canvas
* generate a bitmap of the canvas
The problem for me is, that it must be done in a background thread without drawing a view.
I hope you understand me.
You can use the code bellow to achive it. Where smallBitmap is your original image and bigBitmap is the final image:
Bitmap bigBitmap = Bitmap.createBitmap(width, height , Bitmap.Config.ARGB_8888);
canvas = new Canvas(bigBitmap);
canvas.drawBitmap(smallBitmap, left, top, new Paint());
Regards.
This should do the trick.
Create a thread and in that thread object:
Create a new bitmap.
Create a canvas based on that bitmap.
Draw your bitmap to that canvas
and voila!
I hope this helps.
Is there a way to do it? I d like to save the canvas screen as a Bitmap object, and then draw it again, to the screen.
You can construct a Canvas passing in a Bitmap onto which the canvas will draw. See http://developer.android.com/reference/android/graphics/Canvas.html#Canvas(android.graphics.Bitmap)
You need to construct a Bitmap appropriately sized to the view into which you want to draw.
Just guessing here, but if you are doing this because you want to draw off screen then draw the bitmap on all at once you might also look at SurfaceHolder/SurfaceView.
I am trying to create a bitmap from a View that is not displayed yet to set it as a texture with OpenGL in android.
The problem is that when I create my bitmap the layout parameters of my View have 0 value cause the onLayout() function has not been called yet.
Is there a way to "simulate" a layout or do a "background layout" to get the right layout params ?
I was thinking about a Frame layout having two views, the background one would be used to create my bitmap as the layout would have been done.
Thanks.
You indeed need to layout your View before drawing it into a Bitmap. Simply call
myView.measure(...);
then
myView.layout(0, 0, myView.getMeasuredWidth(), myView.getMeasuredHeight());
I have posted an example on how to do this in one of the following presentations: http://www.curious-creature.org/2010/12/02/android-graphics-animations-and-tips-tricks/
So, some edits after the question was clarified :)
I suggest you create the bitmap independently of the view, then scale it to the same size as the view once the view is created. Create an arbitrary size bitmap that allows you to render what you want to it ..
// This in some class that renders your bitmap independently, and can be
// queried to get the bitmap ...
Bitmap b = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_4444);
// render something to your bitmap here
Then after your view is created, take the precreated bitmap and rescale it to the right size (I've not actually checked this by compiling it -- might be errors):
Rect original = new Rect(0, 0, 100, 100);
RectF destination = new RectF(0.0, 0.0, (float)myView.getWidth(), (float)myView.getHeight());
Canvas canvas = new Canvas();
canvas.drawBitmap(myRenderingClass.b, original, destination, null);
myView.draw(canvas);
Is it possible to manipulate images using canvas? How do we get the image onto the canvas?
#Override
protected void onDraw(Canvas canvas) {
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
Bitmap mBitmap = bitmap.copy(bitmap.getConfig(), true);
canvas = new Canvas(mBitmap);
Matrix matrix = new Matrix();
canvas.drawBitmap(mBitmap, matrix, mPaint);
}
I'm unable to see the image on the screen. canvas.drawBitmap() shouldn't be necessary since I'm using the constructor and passing mBitmap.
Yes you can, but you don't "get the image onto the Canvas," a Canvas is just an interface to draw onto a Bitmap. To do so, simply create a Canvas and give a reference to your mutable Bitmap:
Canvas c = new Canvas(myBitmap);
Very easy :)
You shouldn't do this in your onDraw method. Try to create an ImageView that should display the image and then set the bitmap via setImageBitmap(bitmap).
In general you are doing somethings wrong in your code.
Loading an image every time something should be drawn to the screen will slow down your application a lot. Try to load the image only once and then just edit and set it to the imageview.
You are assigning a new Canvas to the parameter you got. But this won't change anything on the screen. Think of it like somebody puts a paper in front of you and says:"Please write your message on the paper". Now you take another blank paper and write on it. But the other person only knows about his paper and will use this paper to read your message.