Can I draw with anti-aliasing on canvas?

I need my circles and line have smooth edges.

Can I draw with antialiasing on canvas?

What is the difference between Rect and RectF in the Android SDK?

Rect and RectF in Android SDK

The code for drawing an arrow with *Style: Fill* is given below: 

    paint.setColor(Color.parseColor(&quot;#bdc0dc&quot;));
    paint.setStyle(Style.FILL);
    canvas.drawPath(arrowPath, paint);
    paint.setColor(Color.BLACK);
    paint.setStyle(Style.STROKE);
    paint.setStrokeWidth(2);
    canvas.drawPath(arrowPath, paint);

And the output I obtain is this : 

![enter image description here][1]

Now what I want do is set style to Gradient(Style.gradient not present in android...) to obtain the arrow similar to the image given below : 

![enter image description here][2]

How do i do it ? I tried adding style in style.xml but was unable to add gradient there as it accepts item as parameter..


  [1]: http://i.stack.imgur.com/jc1k2.png
  [2]: http://i.stack.imgur.com/pWXVJ.png

How to set gradient style to paint object?

I am trying to develop an app on canvas,I am drawing a bitmap on the canvas. After drawing, I am trying to convert into bitmap image.

Can anyone give me a suggestion?

converting a canvas into bitmap image in android

I have two points in the canvas, now I&#39;m able to draw a line between those points like this below image by using 

This code `canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);`
![enter image description here][1]

I want to draw the arc between two points like below image.

![enter image description here][2]

How can I draw like this.


  [1]: http://i.stack.imgur.com/FyMi3.png
  [2]: http://i.stack.imgur.com/he2zj.png

How to draw Arc between two points on the Canvas?

I&#39;m trying to display a text using the code below.
The problem is that the text is not centered horizontally.
When I set the coordinates for `drawText`, it sets the bottom of the text at this position. I would like the text to be drawn so that the text is centered also horizontally.

This is a picture to display my problem further:

[![Screenshot][1]][2]

    @Override
    protected void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		super.onDraw(canvas);
		//canvas.drawRGB(2, 2, 200);
		Paint textPaint = new Paint();
		textPaint.setARGB(200, 254, 0, 0);
		textPaint.setTextAlign(Align.CENTER);
		textPaint.setTypeface(font);
		textPaint.setTextSize(300);
		canvas.drawText(&quot;Hello&quot;, canvas.getWidth()/2, canvas.getHeight()/2  , textPaint);
	}

  [1]: http://i.stack.imgur.com/vEJNbm.png
  [2]: http://i.stack.imgur.com/vEJNb.png

Android Center text on canvas

Any straight forward way to measure the height of text?
The way I am doing it now is by using Paint&#39;s `measureText()` to get the width, then by trial and error finding a value to get an approximate height. I&#39;ve also been messing around with `FontMetrics`, but all these seem like approximate methods that suck.

I am trying to scale things for different resolutions. I can do it, but I end up with incredibly verbose code with lots of calculations to determine relative sizes. I hate it! There has to be a better way.

Measuring text height to be drawn on Canvas ( Android )

Is there a method which returns the width ( in pixels ) of a text to be drawn on an Android canvas using the drawText() method according to the Paint used to draw it?

Measuring text width to be drawn on Canvas ( Android )

A hopefully quick question, but I can&#39;t seem to find any examples... I&#39;d like to write multi-line text to a custom `View` via a `Canvas`, and in `onDraw()` I have:

    ...
    String text = &quot;This is\nmulti-line\ntext&quot;;
    canvas.drawText(text, 100, 100, mTextPaint);
    ...

I was hoping this would result in line breaks, but instead I am seeing cryptic characters where the `\n` would be.

Any pointers appreciated.

Paul

Draw multi-line text to Canvas

I need to build a project for drawing on canvas by fingers.

How to get the touch event and motion event of my finger and then draw?


Draw in Canvas by finger, Android

I&#39;m struggling to understand the process of drawing to `SurfaceView` and therefore the whole `Surface`/`Canvas`/`Bitmap` system, which is used in Android.

I&#39;ve read all articles and API documentation pages, which I was able to find on android-developers site, a few tutorials of android graphics, LunarLander source code and [this question][1].

Please tell me, which of these statements are true, which are not, and why.

1. `Canvas` has its own `Bitmap` attached to it. `Surface` has its own `Canvas` attached to it.
2. All `View`&#39;s of window share the same `Surface` and thus share the same `Canvas`.
3. `SurfaceView` is subclass of `View`, which, unlike other `View`&#39;s subclasses and `View` itself, has its own `Surface` to draw in.

There is also one additional question:

 - Why is there a need for a `Surface` class, if there is already a `Canvas` for high-level operations with bitmap. Give an example of a situation where `Canvas` is non-suitable for doing work which `Surface` can do.

  [1]: https://stackoverflow.com/questions/3370212/relationship-between-surface-and-canvas-android

Understanding Canvas and Surface concepts

I&#39;d like to create an empty bitmap and set a canvas to that bitmap and then draw any shape on the bitmap.



Creating an empty bitmap and drawing though canvas in Android

how to draw empty rectangle with etc. borderWidth=3 and borderColor=black and part within rectangle don&#39;t have content or color. Which function in Canvas to use

    void drawRect(float left, float top, float right, float bottom, Paint paint)

    void drawRect(RectF rect, Paint paint)

    void drawRect(Rect r, Paint paint)

Thanks.

I try this example

    Paint myPaint = new Paint();
    myPaint.setColor(Color.rgb(0, 0, 0));
    myPaint.setStrokeWidth(10);
    c.drawRect(100, 100, 200, 200, myPaint);

It draws rectangle and fill it with black color but I want just &quot;frame&quot; around
like this image:     

![enter image description here][1]


  [1]: http://i.stack.imgur.com/2aUXE.png

Android canvas draw rectangle

How can I get an image to the canvas in order to draw on that image?

Drawable image on a canvas

I have a view, I&#39;m drawing with the Canvas object in the onDraw(Canvas canvas) method. My code is:

    Paint paint = new Paint();
    paint.setColor(Color.WHITE);
    paint.setStyle(Style.FILL);
    canvas.drawPaint(paint);
    
    paint.setColor(android.R.color.black);
    paint.setTextSize(20);
    canvas.drawText(&quot;Some Text&quot;, 10, 25, paint);

The problem is the text doesn&#39;t show through the background, what am I doing wrong? If I remove the canvas.drawPaint(paint) and paint.setColor(android.R.color.black) you can see the text on the screen.....

Android Canvas.drawText

In order to make a simple game, I used a template that draws a canvas with bitmaps like this:

    private void doDraw(Canvas canvas) {
        for (int i=0;i&lt;8;i++)
            for (int j=0;j&lt;9;j++)
                for (int k=0;k&lt;7;k++)   {
        canvas.drawBitmap(mBits[allBits[i][j][k]], i*50 -k*7, j*50 -k*7, null); } }
(The canvas is defined in &quot;run()&quot; / the SurfaceView lives in a GameThread.)

My first question is how do I clear (or redraw) the _whole_ canvas for a new layout?&lt;br&gt;
Second, how can I update just a part of the screen? &lt;br&gt;&lt;br&gt;

    // This is the routine that calls &quot;doDraw&quot;:
    public void run() {
        while (mRun) {
            Canvas c = null;
            try {
                c = mSurfaceHolder.lockCanvas(null);
                synchronized (mSurfaceHolder) {
                    if (mMode == STATE_RUNNING) 
                        updateGame();
                    doDraw(c);          }
            } finally {
                if (c != null) {
                    mSurfaceHolder.unlockCanvasAndPost(c);  }   }   }       }

Android, canvas: How do I clear (delete contents of) a canvas (= bitmaps), living in a surfaceView?

So I&#39;m drawing this triangle in android maps using the code below in my draw method:

    paint.setARGB(255, 153, 29, 29);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setAntiAlias(true);

    Path path = new Path();
    path.moveTo(point1_returned.x, point1_returned.y);
    path.lineTo(point2_returned.x, point2_returned.y);
    path.moveTo(point2_returned.x, point2_returned.y);
    path.lineTo(point3_returned.x, point3_returned.y);
    path.moveTo(point3_returned.x, point3_returned.y);
    path.lineTo(point1_returned.x, point1_returned.y);
    path.close();
        	
    canvas.drawPath(path, paint);

The pointX_returned are the coordinates which I&#39;m getting from the fields. They are basically latitudes and longitudes.
The result is a nice triangle but the insider is empty and therefore I can see the map. Is there a way to fill it up somehow? 



How to draw a filled triangle in android canvas?

I sometimes have seen in examples where the coloring in Android is done as #FF191919. I mean an eight-digit hex number. But it should only be a six-digit number. How are they related?

If I want to convert a six-digit number to a eight-digit number, how can I do it? I mean convert #424242 to a eight-digit number coloring? What are the the details?




Hex colors in Android are sometimes eight digits. How? What is the difference between #FFFFFF and #FFFFFF00?

I want a Bitmap icon with bold text to draw it on map. I have a snippet to write text on image:

    Bitmap icon = BitmapFactory.decodeResource(PropertyMapList.this.getResources(),
            R.drawable.location_mark);
	TextPaint paint = new TextPaint();
	paint.setColor(Color.BLACK);
	paint.setTextSize(14);
	paint.setFakeBoldText(true);
	//paint.setTextAlign(Align.CENTER);
	Bitmap copy = icon.copy(Bitmap.Config.ARGB_8888, true); 
	Canvas canvas = new Canvas(copy);
	//canvas.drawText(jsonObj.getString(&quot;district_name&quot;), 5, canvas.getHeight()/2, paint);
	String districtName = jsonObj.getString(&quot;district_name&quot;);
	StaticLayout layout = new StaticLayout((districtName.length()&gt;25 ? districtName.substring(0, 24)+&quot;..&quot;:districtName)+&quot;\n&quot;+jsonObj.getString(&quot;total_properties&quot;), paint, canvas.getWidth()-10,Layout.Alignment.ALIGN_CENTER, 1.3f, 0, false);
	canvas.translate(5, canvas.getHeight()/2); //position the text
	layout.draw(canvas);

`setFakeBoldText(true)` doesn&#39;t work for me. I would like the text drawn on the Bitmap to be bolded.

How do I draw bold text on a Bitmap?

I want to draw circle by canvas. Here is my code:

[MyActivity.java]:

    public class MyActivity extends Activity 
    {
     public void onCreate(Bundle savedInstanceState) 
       {
          ...
          setContentView(new View(this,w,h));
       }
            
    }

[View.java]:

    public class View extends SurfaceView
    {
        public View(Context context, int w, int h)
        {
            super(context);
            Canvas grid = new Canvas(Bitmap.createBitmap(h,w, Bitmap.Config.ARGB_8888));
            grid. drawColor(Color.WHITE);
            Paint paint = new Paint();
            paint.setStyle(Paint.Style.FILL);
            grid.drawCircle(w/2, h/2 , w/2, paint);
        }
    }

So I have just black screen without circle.
Why it does not work? How to fix it?


How to draw circle by canvas in Android?

I found a function for rectangles with all 4 corners being round, but I want to have just the top 2 corners round. What can I do?

    canvas.drawRoundRect(new RectF(0, 100, 100, 300), 6, 6, paint);

How to use android canvas to draw a Rectangle with only topleft and topright corners round?

I am using the onScroll method of GestureDetector.SimpleOnGestureListener to scroll a large bitmap on a canvas. When the scroll has ended I want to redraw the bitmap in case the user wants to scroll further ... off the edge of the bitmap, but I can&#39;t see how to detect when the scroll has ended (the user has lifted his finger from the screen).

e2.getAction() always seems to return the value 2 so that is no help.
e2.getPressure seems to return fairly constant values (around 0.25) until the final onScroll call when the pressure seems to fall to about 0.13. I suppose I could detect this reduction in pressure, but this will be far from foolproof.

There must be a better way: can anyone help, please?

Android: How to detect when a scroll has ended

The [documentation][1] is pretty vague as to what is actually happening when these methods are used.  Can someone explain how Matrix actually affects the Bitmap that it&#39;s being set to? They use the term concatenate in there, but I&#39;m unclear on how that term applies to coordinate data (having only used it in regard to string manipulation before).


  [1]: http://developer.android.com/reference/android/graphics/Matrix.html

Looking for an explanation of post/pre/set Translate (in Matrix object) and how to use them

I would like to have a better understanding of how the components of Android&#39;s (2D) Canvas drawing pipeline fit together.

For example, how do [XferMode](http://developer.android.com/reference/android/graphics/Xfermode.html), [Shader](http://developer.android.com/reference/android/graphics/Shader.html), [MaskFilter](http://developer.android.com/reference/android/graphics/MaskFilter.html) and [ColorFilter](http://developer.android.com/reference/android/graphics/ColorFilter.html) interact? The reference docs for these classes are pretty sparse and the docs for [Canvas](http://developer.android.com/reference/android/graphics/Canvas.html) and [Paint](http://developer.android.com/reference/android/graphics/Paint.html) don&#39;t really add any useful explanation.

It&#39;s also not entirely clear to me how drawing operations that have intrinsic colors (eg: `drawBitmap`, versus the &quot;vector&quot; primitives like `drawRect`) fit into all of this -- do they always ignore the `Paint`&#39;s color and use use their intrinsic color instead?

I was also surprised by the fact that one can do something like this:

    Paint eraser = new Paint();
    eraser.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
    canvas.drawOval(rectF, eraser);

This erases an oval. Before I noticed this my mental-model was that drawing to a canvas (conceptually) draws to a separate &quot;layer&quot; and then that layer is composed with the Canvas&#39;s Bitmap using the Paint&#39;s transfer mode. If it were as simple as that then the above code would erase the entire Bitmap (within the clipping region) as CLEAR *always* sets the color (and alpha) to 0 regardless of the source&#39;s alpha. So this implies that there&#39;s an additional sort of masking going on to constrain the erasing to an oval.

I did find the [API demos](http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/graphics/index.html) but each demo works &quot;in a vacuum&quot; and doesn&#39;t show how the thing it focusses on (eg: XferModes) interacts with other stuff (eg: ColorFilters).

With enough time and effort I could empirically figure out how these pieces relate or go decipher the source, but I&#39;m hoping that someone else has already worked this out, or better yet that there&#39;s some actual documentation of the pipeline/drawing-model that I missed.

This question was inspired by seeing the code in [this answer to another SO question](https://stackoverflow.com/questions/4560265/android-edit-bitmap-channels/4632210#4632210).

Update
-

While looking around for some documentation it occurred to me that since much the stuff I&#39;m interested in here seems to be a pretty thin veneer on top of [skia](http://code.google.com/p/skia/), maybe there&#39;s some skia documentation that would be helpful. The best thing I could find is [the documentation for `SkPaint`](http://code.google.com/p/skia/wiki/SkPaint) which says:

&gt; There are 6 types of effects that can
&gt; be assigned to a paint:
&gt; 
&gt; - SkPathEffect - modifications to the geometry (path) before it generates an
&gt; alpha mask (e.g. dashing)
&gt; - SkRasterizer - composing custom mask layers (e.g. shadows)
&gt; - SkMaskFilter - modifications to the alpha mask before it is colorized and
&gt; drawn (e.g. blur, emboss)
&gt; - SkShader - e.g. gradients (linear, radial, sweep), bitmap patterns
&gt; (clamp, repeat, mirror)
&gt; - SkColorFilter - modify the source color(s) before applying the xfermode
&gt; (e.g. color matrix)
&gt; - SkXfermode - e.g. porter-duff transfermodes, blend modes

It isn&#39;t stated explicitly, but I&#39;m guessing that the order of the effects here is the order they appear in the pipeline.


How do the pieces of Android&#39;s (2D) Canvas drawing pipeline fit together?

I am creating a pixel-hunting game. So my activity shows an ImageView. And I want to create a hint &quot;show me where is the object&quot;. For this I need to blur whole image except a circle around a point where the object is located. Instead of blur I can show a just semitransparent black background.
There is there is no problem to draw a semitransparent rectangle on the Canvas.
But I don&#39;t know how to crop a transparent circle from it. 
The result should look like like this:
![enter image description here][1]


  [1]: http://i.stack.imgur.com/tcpdJ.jpg

Please help me to achieve same result on Android SDK.

Android canvas: draw transparent circle on image

I want to draw text on `canvas` of certain width using `.drawtext`

For example, the width of the text should always be `400px` no matter what the input text is. 

If input text is longer it will decrease the font size, if input text is shorter it will increase the font size accordingly.

android canvas drawText set font size from width?

I have an Android project where I should make Apples fall. The apples are painted in a Rect. So I created a function that change the Rect position and repaint. Here&#39;s my function :

    private void updateApplesPosition() {
        for(Rect rect:fallingDownFruitsList)
            rect.set(rect.left, rect.top +10, rect.right, rect.bottom +10);
    }

I have a problem : the Apples don&#39;t fall but go from right to left. To make the apples fall I changed the code by this :

    private void updateApplesPosition() {
        for(Rect rect:fallingDownFruitsList)
            rect.set(rect.left+10, rect.top, rect.right+10, rect.bottom);
    }

What does top, left, right and bottom mean in Android Rect object

Is there any way in Android to draw a filled rectangle with say a black border. My problem is that the canvas.draw() takes one paint object, and to my knowledge the paint object can&#39;t have a different color for the fill and the stroke. Is there a way around this?

All Android Canvas Solutions on Gang of Coders

Total of 28 Android Canvas Solutions