I have an ImageView from which I want to copy a piece of it in the shape of a circle that I can then re-display to the user at a larger than original size to simulate a zoom effect. Would I use bitmaps for that? Thanks.
Yes.... you can try to get a Bitmap that represents the ImageView you are working with. Before, you have to enable the caching (by invoking the setDrawingCacheEnabled(true) method). To get the Bitmap representation of the image, you can use the getDrawingCache() method.
Once you get that Bitmap, you can resize it or make any other changes you want. Then, you can create a Rect object with the portion of the bitmap you want to draw, then you draw that rect using this method: drawBitmap(Bitmap, Rect origin, Rect destination, Paint).
Related
I need to save a number of formatted circles to a Bitmap whenever a button is pushed, and then draw those circles to the canvas. I was looking around, but had a great deal of trouble finding resources on how to save a shape I had created that was not an already created resource file. Any advice on how to go about this would be appreciated.
Say you are in your custom view, but it should work also with a OnTouchListener in any view.
Create a mutable bitmap with Bitmap.createBitmap() with the same width and height of your view
use your logic for getting information of the circles, for example you can use onTouchEvent() to get the coordinates of you finger(s)
with this information you can use Bitmap.setPixel() to save it to the bitmap
optional, onDraw() you can draw your bitmap with Canvas.drawBitmap()
In case you need to draw shapes to the bitmap you can create a new Canvas(bitmap) and draw on this canvas: the pixels will be set on the bitmap.
Suppose, we've got a display sized 100x100, an image 100x50, and I want to enlarge that image so that it has the same height as the screen does. So the image will be 200x100. After that I want to make the animation of image movement to the left and to the right. I've found 2 ways of the realization of my task:
To create a new image using Bitmap.createScaledBitmap(). But the
image created this way will occupy twice more RAM.
To use matrix.setScale() in every onDraw(). But this works very
slow. Is there any other better solution?
The second method is slow because you calculate your "matrix" on every frame! Since your matrix is always the same thing and it does not change, you can pre-calculate your matrix and save it as a "field" in you class, then just use this function to draw it on screen:
canvas.drawBitmap(Bitmap bitmap, Matrix matrix, Paint paint)
It should be fast enough. The other option is to use:
canvas.drawBitmap(Bitmap bitmap, Rect src, RectF dst, Paint paint)
Again, try to pre-calculate stuff as much as possible. In this case, pre-calc src and dst rectangles.
I would like to draw text on a canvas using the Canvas.drawText call for a game application, and later be able to scale it as if it was a bitmap object. I do not want to dynamically change its font size, but I want to scale it applying an affine transform.
Is it possible? I cannot find an adequate API call in the documentation.
Thank you!
Using Matrix you can scale it and that apply the matrix tranformation to the canvas with Canvas.concat(Matrix m) . Do this before drawing the text onto the canvas.
Once it's on the Canvas, it's not a separate object that you can do anything to. What you can do is use the Canvas as an API for drawing to a bitmap:
Create a Bitmap.
Create a Canvas backed by that Bitmap.
Draw your text into the Canvas.
Hang on to your Bitmap and do whatever you want with it.
I am trying to subclass ImageView and draw something on Bitmap. However I cannot find a way to get the Rect in which Bitmap is drawn. I can only get the Rect in which ImageView is drawn by getDrawingRect(Rect) method of ImageView. Below is an illustration of what I want to get:
The Rect I want is the blue one. Thanks in advance.
The given image will be drawn in the ImageView based on the attributes given e.g., height, width, scaling factors, etc.
So that the getDrawingRect() method giving the entire area of ImageView. If you change the drawable inside ImageView the blue colored area may change based on the image properties and imageview properties. But the yellow colored area won't change because it is fixed and based on the ImageView only, its independent of image displayed.
I think no chance to get the Rect of bitmap drawn. Don't think my answer is 100% correct, it is just a suggestion only.
You may get information about blue colored area from Drawing Cache. Try it once.
I hope it may help you.
I would like to create a 'graph paper' look to the Bitmap I am drawing via a Canvas, and trying to figure out the best way to do this.
I can't pass a source Bitmap containing the graph paper background to the Canvas constructor, as I am getting the Canvas in a SurfaceView via the .lockCanvas() call.
Some solutions I've tried:
I've tried implementing this solution in my SurfaceView's Thread.run(), but the issue I believe is when the BitmapDrawable is converted to a Bitmap... it loses the tiling properties.
canvas = mSurfaceHolder.lockCanvas(null);
BitmapDrawable TileMe = new BitmapDrawable(BitmapFactory.decodeResource(getResources(), R.drawable.editor_graph));
TileMe.setTileModeX(Shader.TileMode.REPEAT);
TileMe.setTileModeY(Shader.TileMode.REPEAT);
Bitmap b = TileMe.getBitmap();
canvas.drawBitmap(b, 0, 0, null);
If I use the Canvas.drawBitmap method that takes a destination RectF as a parameter, it looks like the bitmap will be tiled to fill the RectF... but how do I declare a RectF reliably that fills the entire view area?
Setting the Activities background to the desired graph paper look also doesn't work, as the bitmap/canvas layout is opaque and blocks that from being seen.
Any ideas how to achieve this?
You have two easy solutions:
Either use a BitmapDrawable, but instead of extracting the Bitmap, just call BitmapDrawable.draw(Canvas). Don't forget to set the drawable's bounds to fill your drawing area.
Create a Paint with a BitmapShader and draw a rectangle with it (this is basically what BitmapDrawable does).
I'm sure there is a way to get a tiled effect using a SurfaceView. Unfortunately, it looks like you can't use the BitmapDrawable with a canvas. So you would probably have to implement you own custom tiling method by creating your own series of Rect's on the Canvas and drawing a scaled bitmap to each one.
It honestly wouldn't be that hard. Just get the width/height of the view, and create an array of Rect's based on this data that you will draw the Bitmap to.
Alternatively, if you don't need to make modifications to the actual tiled background on the fly, just draw it as a background and draw the SurfaceView on top of it. That post you linked provided multiple solutions to tiling a BitmapDrawable that you could implement.