This is a Picasso Transformation used to make images look like speech bubbles.

ExampleUsage.java

//In my case I first resize the image to a max width of 300dp as I'm displaying in a list and want them to look uniform
//Then for the margin and raidus measurements, I convert from dp to px, so that it appears the same on different screens.
Picasso.with(mContext)
                    .load(imageUrl)
                    .resize((int)UiUtils.dpToPx(mContext, 300), 0)
                    .transform(new SpeechBubbleTransform((int)UiUtils.dpToPx(mContext, 8), (int)UiUtils.dpToPx(mContext,12), SpeechBubbleTransform.Corner.BOTTOM_LEFT))
                    .into(holder.mIvPhotoMessage);

SpeechBubbleTransform.java

public static class SpeechBubbleTransform implements Transformation {

        public enum Corner {
            BOTTOM_LEFT,
            BOTTOM_RIGHT
        }

        private final int mMargin;
        private final int mCornerRadius;
        private final Corner mCorner;

        /**
         * Transforms an image to look like a speech bubble, i.e. rounded corners and a tail on the bottom left or right.
         * @param margin The size of the area around the image that will be cropped. This basically dictates how big the tail will be.
         * @param cornerRadius Radius of rounded corners
         * @param corner Which corner the tails will be placed on. BOTTOM_LEFT or BOTTOM_RIGHT
         */
        public SpeechBubbleTransform(int margin, int cornerRadius, Corner corner) {
            mMargin = margin;
            mCornerRadius = cornerRadius;
            mCorner = corner;
        }

        @Override
        public Bitmap transform(Bitmap source) {
            Bitmap output = Bitmap.createBitmap(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(output);

            int startX, startY, x1, y1, x2, y2, x3, y3, x4, y4;

            // initialise coordinates based on what corner is set
            switch (mCorner) {
                case BOTTOM_LEFT:
                    startX = mMargin * 3;
                    startY = source.getHeight() - mMargin;
                    x1 = (int)(mMargin * 2.5);
                    y1 = source.getHeight();
                    x2 = 0;
                    y2 = source.getHeight();
                    x3 = mMargin;
                    y3 = source.getHeight() - mMargin;
                    x4 = mMargin;
                    y4 = source.getHeight() - mMargin * 3;
                    break;
                case BOTTOM_RIGHT:
                default:
                    startX = source.getWidth() - mMargin * 3;
                    startY = source.getHeight() - mMargin;
                    x1 = source.getWidth() - (int)(mMargin * 2.5);
                    y1 = source.getHeight();
                    x2 = source.getWidth();
                    y2 = source.getHeight();
                    x3 = source.getWidth() - mMargin;
                    y3 = source.getHeight() - mMargin;
                    x4 = source.getWidth()- mMargin;
                    y4 = source.getHeight() - mMargin * 3;
                    break;
            }

            Paint tailPaint = new Paint();
            tailPaint.setAntiAlias(true);
            tailPaint.setShader(new BitmapShader(source, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP));

            Path tail = new Path();
            tail.setFillType(Path.FillType.EVEN_ODD);
            tail.moveTo(startX, startY);
            tail.quadTo(x1 ,y1, x2, y2);
            tail.quadTo(x3, y3, x4, y4);
            tail.close();



            final Paint paint = new Paint();
            paint.setAntiAlias(true);
            paint.setShader(new BitmapShader(source, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP));
            canvas.drawRoundRect(new RectF(mMargin, mMargin, source.getWidth() - mMargin, source.getHeight() - mMargin), mCornerRadius, mCornerRadius, paint);

            canvas.drawPath(tail, tailPaint);

            if (source != output) {
                source.recycle();
            }

            return output;
        }

        @Override
        public String key() {
            return "bubble";
        }
    }