Develop Reference

How to add stroke/border to transparent png image in android?

I have transparent images like shapes,letters which I'm fetch from gallery so I need to give them stroke/outline with black color, I can set border but It's set to whole bitmap like left,right,top and bottom.
Same thing we can do with photoshop is giving outerstroke to image but I want to achieve that in android.
I tried this and this It's give border, But what I want to do is like below
sample image
Original Image
I want like this -->
Does this possible in android?

I have an temporary solution like this
int strokeWidth = 8;
Bitmap originalBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.flower_icon);
Bitmap newStrokedBitmap = Bitmap.createBitmap(originalBitmap.getWidth() + 2 * strokeWidth, originalBitmap.getHeight() + 2 * strokeWidth, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(newStrokedBitmap);
float scaleX = newStrokedBitmap.getWidth() / originalBitmap.getWidth();
float scaleY = newStrokedBitmap.getHeight() / originalBitmap.getHeight();
Matrix matrix = new Matrix();
matrix.setScale(scaleX, scaleY);
canvas.drawBitmap(originalBitmap, matrix, null);
canvas.drawColor(Color.WHITE, PorterDuff.Mode.SRC_ATOP); //Color.WHITE is stroke color
canvas.drawBitmap(originalBitmap, strokeWidth, strokeWidth, null);
Firstly create a new bitmap with stroke size on left, right, bottom and top.
Secondly a little bit scale bitmap and draw scaled bitmap on newly created bitmap canvas.
Draw a color (your stroke color) with PorterDuff mode SRC_ATOP override original bitmap position with stroke color.
Finally draw your original bitmap on newly create bitmap canvas.

Is there a way to not stretch the Bitmap when using Matrix.polyToPoly() on a bitmap?

I'm trying to do perspective transformation on my bitmap with a given quadrilateral. However, the Matrix.polyToPoly function stretches not only the part of the image I want but also the pixels outside the given area, so that a huge image is formed in some edge cases which crashes my app because of OOM.
Is there any way to sort of drop the pixels outside of the said area to not be stretched?
Or are there any other possibilities to do a perspective transform which is more memory friendly?
I`m currenty doing it like this:
// Perspective Transformation
float[] destination = {0, 0,
width, 0,
width, height,
0, height};
Matrix post = new Matrix();
post.setPolyToPoly(boundingBox.toArray(), 0, destination, 0, 4);
Bitmap transformed = Bitmap.createBitmap(temp, 0, 0, cropWidth, cropHeight, post, true);
where cropWidth and cropHeight are the size of the bitmap (I cropped it to the edges of the quadrilateral to save memory) and temp is said cropped bitmap.

Thanks to pskink I got it working, here is a post with the code in it:
Distorting an image to a quadrangle fails in some cases on Android

Rotating a Bitmap around a point NOT center to bitmap

I have a bitmap that I would like to rotate about a point on a canvas. The point I want to rotate it about is not the center of the bitmap. I am using a matrix. Here is an example of what I have.
Bitmap image = ContentManager.getInstance().getImage(imageId);
Matrix matrix = new Matrix();
matrix.setTranslate(-image.getWidth()/2f, -image.getHeight()/2f);
matrix.postRotate(rotationDegrees);
matrix.postTranslate(x / scaleX, y / scaleY);
matrix.postScale(scaleX, scaleY);
paint.setAlpha(alpha);
canvas.drawBitmap(image, matrix, paint);
I want to manipulate this code slightly to not rotate around the bitmap's center point but a different point. To illustrate more clearly I have created this picture:
.
I have tried everything I can think of from setting
matrix.setTranslate(-image.getWidth()/2f, -image.getHeight()/2f);
to
matrix.setTranslate(pivotPoint.x, pivotPoint.y);
and a lot of other stuff. The result is the bitmap is always way off from where I expected it. (eg. rotate it about the center of the screen 90 degrees would put the bitmap 90 degrees from where it was and consequently would be rotated.) The bitmap always seems to rotate about its center point and then ends up in a random spot on the screen.

After much messing around and find this very difficult or buggy, not sure which, found the easiest solution to this is to find the new center of the bitmap and drop the image there instead, seem more complicated but it works where plain rotation/translation wasn't.
float angle;
float radius;
Bitmap wheelSelectBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);
Matrix matrix = new Matrix();
Point pivotPoint = new Point();
pivotPoint.set(pivotPoint.x, pivotPoint.y)
Point newCenter = new Point();
newCenter.set((int)(pivotPoint.x + (radius * Math.cos(angle)), (int)(pivotPoint.y - (radius * Math.sin(angle)));
matrix.postTranslate(newCenter.x - (bitmap.getWidth()/2f), newCenter.y - (bitmap.getHeight()/2f));
matrix.postRotate(angle, newCenter.x, newCenter.y);
Bitmap rotatedBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), null, true);
canvas.drawBitmap(bitmap, matrix, null);
This might not be perfect but working this way solved the problem for me and stopped bitmaps flying around all over the shop. It also rotates clockwise by default unlike your diagram so just use -angle for counter-CW. Not sure what is going on here as this code definitely failed to get the desired effect for me:
matrix.postTranslate(pivotPoint.x, pivotPoint.y);
matrix.postRotate(angle);
matrix.postTranslate(radius - (bitmap.getWidth()/2f), -bitmap.getHeight()/2f);
Cant see what is wrong with logic here ? But in my case the bitmap was not visible in the view here.

When rotating an object, it will rotate around the origin (upper left corner). You'll want to first translate the bitmap so the pivot point becomes (0, 0), rotate the bitmap then translate back to it's original position.
you could try something like this:
matrix.setTranslate(-px, -py);
matrix.postRotate(rotationDegrees);
matrix.setTranslate(px, py);
// Then do other things.

Rotate an imageView at an angle using Seekbar

I simply want to rotate an image from min to max. But for that i have used multiple images to show Progress. Can some one suggest me a way to use a single image. which can rotate at an angle from min to max.
I know there are two possible ways to achieve it.
Using Animation Classes
Custom View
I simply want to rotate this image using SeekBar in any number of steps.
How can i achieve this?
To roate an Image
private void rotate(float degree) {
final RotateAnimation rotateAnim = new RotateAnimation(0.0f, degree,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
rotateAnim.setDuration(0);
rotateAnim.setFillAfter(true);
imgview.startAnimation(rotateAnim);
}
Second Approach
imageView.setRotation(angle); // but requires API >= 11
I can use Matrix
Matrix matrix = new Matrix();
imageView.setScaleType(ScaleType.MATRIX); //required
matrix.postRotate((float) angle, pivX, pivY);
imageView.setImageMatrix(matrix);
How can i set Start and end angle to SeekBar min and max respectively. Which approach is better and Whether i must put it in FrameLayout to let it rotate freely.

You can do this way :
// load the origial BitMap (500 x 500 px)
Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(),
R.drawable.android);
int width = bitmapOrg.width();
int height = bitmapOrg.height();
// createa matrix for the manipulation
Matrix matrix = new Matrix();
// rotate the Bitmap
matrix.postRotate(45);
// recreate the new Bitmap
Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, width, height, matrix, true);
// make a Drawable from Bitmap to allow to set the BitMap
// to the ImageView, ImageButton or what ever
BitmapDrawable bmd = new BitmapDrawable(resizedBitmap);
// set the Drawable on the ImageView
imageView.setImageDrawable(bmd);
For details check this out.
http://www.anddev.org/resize_and_rotate_image_-_example-t621.html
matrix.postRotate(45); //here 45 is the degree of angle to rotate

You can use a Matrix as suggested here
Matrix matrix = new Matrix();
imageView.setScaleType(ScaleType.MATRIX); //required
matrix.postRotate((float) angle, pivX, pivY);
imageView.setImageMatrix(matrix);

This would be an infinite rotation but you could spin it however you want.
This view just spins 360 degrees infinitely.
final RotateAnimation R = new RotateAnimation(0, 360, view.getWidth() / 2.0f, view.getHeight() / 2.0f);
R.setRepeatCount(Animation.INFINITE);
R.setDuration(800);
view.startAnimation(R);

Android OutOfMemoryError when trying to rotate an image

I want to display an image on screen (I have an activity that displays an image):
Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
ExifInterface exif = new ExifInterface(imagePath);
int rotation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
int rotationInDegrees = exifToDegrees(rotation);
Matrix matrix = new Matrix();
matrix.preRotate(rotationInDegrees);
bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
The last line throws java.lang.OutOfMemoryError
I don't understand how to do this... I have to create the bitmap at first (BitmapFactory.decodeFile) but when I want to rotate it I have to provide the source bitmap already - how can I avoid it?
Thanks

You can try downsizing the image first before decoding it by adding inSampleSize in the bitmap options. as stated at the document: http://developer.android.com/reference/android/graphics/BitmapFactory.Options.html#inSampleSize
If set to a value > 1, requests the decoder to subsample the original image, returning a smaller image to save memory.
BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 5;
Bitmap bitmap = BitmapFactory.decodeFile(imagePath, options);
Hope that helps.

If you aren't doing any crazy things elsewhere then your image is probably just too big.
You just need to increase your heap. Add this to your manifest file:
android:largeHeap="true"

You cannot rotate the bitmap in place, because the dimensions can be different. I don't know, why it's impossible to load already rotated bitmap.
You can rotate the bitmap in the place of use. When drawing the bitmap, use the rotation matrix to have it drawn with rotation.
Other thing is that you probably should review your app and try to minimize the memory usage. Maybe the bitmaps you use are too big and you should use Options with inSampleSize set to 2 or more.