Develop Reference

Android canvas add stroke and elevation

I am creating a thumbnail from a large image via canvas to use it as marker in google map and how can i add a border (stroke) of 2 dp and also light elevation in my thumbnail
Canvas function
public static Bitmap getCroppedBitmap(Bitmap bitmap) {
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
bitmap.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawCircle(bitmap.getWidth() / 2, bitmap.getHeight() / 2,
bitmap.getWidth() / 2, paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;
}

drawRoundRect in Android not working

I want to draw a rounded rectangle with drawRoundRect method in Android.
void drawRoundRect (RectF rect, float rx, float ry, Paint paint)
I'm using Android Studio, and my testing device use Android 6.0.1, API 23
This is part of my code. It works find when I put zeros in rx and ry.
public void draw(Canvas canvas){
canvas.drawColor(Color.WHITE);
canvas.drawRoundRect(rect, 0, 0, pnt);
}
This draws a black rectangle in my screen.
But when I try to make it rounded,
public void draw(Canvas canvas){
canvas.drawColor(Color.WHITE);
canvas.drawRoundRect(rect, 10, 10, pnt);
}
It draws nothing. This only draws white background....
I tried different numbers like 100, 3, 5, 0.03f etc in rx and ry,
but any numbers bigger than 0 make drawRoundRect() not working.
Is there anything wrong with my code...?

Make sure that coordinates in RectF that is used to draw rounded rectangle are correct. That means: rect.left < rect.right and rect.top < rect.bottom.
It seems that Android 7 corrects wrong coordinates itself and draws desired rounded rectangle, but Android 6 is drawing nothing if there is problem with coordinates.

you can try this we have a little calculation but it works awesomely
private void drawRoundedRect(Canvas canvas, float left, float top, float right, float bottom) {
float radius = getHeight() / 2;
canvas.drawCircle(radius, radius, radius, mainPaint);
canvas.drawCircle(right - radius, radius, radius, mainPaint);
canvas.drawRect(left + radius, top, right - radius, bottom, mainPaint);
}
or you can check this
RectF rect = new RectF(10,10,20,20);
canvas.drawRoundRect(rect , 0, 0, mPaint);

Try this,
Bitmap bitmap = Bitmap.createBitmap(
600, // Width
300, // Height
Bitmap.Config.ARGB_8888 // Config
);
Canvas canvas = new Canvas(bitmap);
canvas.drawColor(Color.WHITE);
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(Color.RED);
paint.setAntiAlias(true);
int offset = 50;
RectF rectF = new RectF(
offset, // left
offset, // top
canvas.getWidth() - offset, // right
canvas.getHeight() - offset // bottom
);
int cornersRadius = 25;
canvas.drawRoundRect(
rectF, // rect
cornersRadius, // rx
cornersRadius, // ry
paint // Paint
);
mImageView.setImageBitmap(bitmap);

You could do this,
RectF rect = new RectF(0f, 0f, width, height);
canvas.drawRoundRect(rect , 0, 0, mPaint);

How to rotate only the canvas behind the text

I have this function that animate the image canvas from resource drawable with text on the front.
I want to rotate the a green "star" only so the text stay intact
The idea is to rotate only the image canvas but no the text.
How do I do that?
This code is for Android Java
private Bitmap writeTextOnDrawable(int drawableId, String text, ImageView imv_promo,boolean isAnim) {
Bitmap bm = BitmapFactory.decodeResource(ctx.getResources(), drawableId).copy(Bitmap.Config.ARGB_8888, true);
Typeface tf = Typeface.createFromAsset(ctx.getAssets(), "RobotoCondensed-Italic.ttf");
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
paint.setColor(ctx.getResources().getColor(R.color.white));
paint.setTypeface(tf);
paint.setTextAlign(Paint.Align.CENTER);
paint.setTextSize(convertToPixels(mContext, 17));
Rect textRect = new Rect();
paint.getTextBounds(text, 0, text.length(), textRect);
Canvas canvas = new Canvas(bm);
//If the text is bigger than the canvas , reduce the font size
if (textRect.width() >= (canvas.getWidth() - 4)) //the padding on either sides is considered as 4, so as to appropriately fit in the text
paint.setTextSize(convertToPixels(mContext, 7)); //Scaling needs to be used for different dpi's
//Calculate the positions
int xPos = (canvas.getWidth() / 2) - 6; //-2 is for regulating the x position offset
int yPos = (int) ((canvas.getHeight() / 2) - ((paint.descent() + paint.ascent()) / 2));
canvas.save();
canvas.rotate((float) 25, xPos, yPos);
canvas.drawText(text, xPos, yPos, paint);
canvas.restore();
Animation animation;
if(isAnim) {
animation = new RotateAnimation(0, 360, canvas.getWidth() / 2, canvas.getHeight() / 2);
animation.setRepeatMode(Animation.RESTART);
animation.setRepeatCount(Animation.INFINITE);
animation.setDuration(20000L);
imv_promo.startAnimation(animation);
}
return bm;
}

Adding a round frame circle on rounded bitmap

Im trying to create a round frame around my bitmap!
With this code im able to make my bitmap round:
public static Bitmap getRoundedCornerBitmap(Bitmap bitmap) {
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap
.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff4242DB;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
final RectF rectF = new RectF(rect);
final float roundPx = bitmap.getWidth()/2;
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
//canvas.drawCircle(0, 0, bitmap.getWidth(), paint);
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;
}
What i've tried is to draw a circle(the outcommented line) with canvas, but It had no result.
Does anyone know how I can add a circular border around it?
EDIT
When I use the line:
canvas.drawCircle(0, 0, bitmap.getWidth(), paint);
The effect is, that 3 corners get rounded but the upper left stays the same(90 degrees)
But I can't see any line or circle!

Update
There now is RoundedBitmapDrawable and a corresponding factory in the Support library I recommend to use that, unless more flexibility is required.
Original Answer
You have to draw the circle after the bitmap. This is what did the trick for me.
int w = bitmap.getWidth();
int h = bitmap.getHeight();
int radius = Math.min(h / 2, w / 2);
Bitmap output = Bitmap.createBitmap(w + 8, h + 8, Config.ARGB_8888);
Paint p = new Paint();
p.setAntiAlias(true);
Canvas c = new Canvas(output);
c.drawARGB(0, 0, 0, 0);
p.setStyle(Style.FILL);
c.drawCircle((w / 2) + 4, (h / 2) + 4, radius, p);
p.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
c.drawBitmap(bitmap, 4, 4, p);
p.setXfermode(null);
p.setStyle(Style.STROKE);
p.setColor(Color.WHITE);
p.setStrokeWidth(3);
c.drawCircle((w / 2) + 4, (h / 2) + 4, radius, p);
return output;
This does of course not include the fancy shadow of your example.
You might want to play around a little bit with the additional pixels.

Align the texts center with the given position

I need to draw a text using
canvas.drawText("1",x,y, paint);
But the problem is that the "text's center" doesn't match with the position I have given,Is there any way I can do the latter.I have done quite a lot of search on the topic,culdn't find any answer.Please help.
Thank You in advance

You'll want to set the alignment on your paint instance:
paint.setTextAlign(Paint.Align.CENTER);
prior to drawing.
See: http://developer.android.com/reference/android/graphics/Paint.html#setTextAlign(android.graphics.Paint.Align)
Edit:
Per your indication that you'd also like it centered vertically, I'd go with an approach similar to this:
paint.setColor(Color.WHITE);
paint.setTextAlign(Align.LEFT);
String text = "Hello";
Rect bounds = new Rect();
float x = 100, y = 100;
paint.getTextBounds(text, 0, text.length(), bounds); // Measure the text
canvas.drawLine(0, y, canvas.getWidth(), y, paint); // Included to show vertical alignment
canvas.drawLine(x, 0, x, canvas.getHeight(), paint); // Included to show horizsontal alignment
canvas.drawText(text, x - bounds.width() * 0.5f, y + bounds.height() * 0.5f, paint); // Draw the text
or, using the center align on the paint:
paint.setColor(Color.WHITE);
paint.setTextAlign(Align.CENTER);
String text = "Hello";
Rect bounds = new Rect();
float x = 100, y = 100;
paint.getTextBounds(text, 0, text.length(), bounds); // Measure the text
canvas.drawLine(0, y, canvas.getWidth(), y, paint); // Included to show vertical alignment
canvas.drawLine(x, 0, x, canvas.getHeight(), paint); // Included to show horizsontal alignment
canvas.drawText(text, x, y + bounds.height() * 0.5f, paint); // Draw the text