Develop Reference

create a mask from bitmap

I have an image as bitmap e.g
I want to create mask programmatically from that bitmap like this
I searched online but did not find any solution.

2003 Java Q and A about Masking Images
The question posed on this website seems similar to yours and the answers should help you out. Their code was written in Java back in 2003, but I believe you are asking about something you plan to program in Android Studio from your tags in I am guessing Java. Your question is kind of vague, but maybe this website will be a good starting point. There are longer solutions, with complete code written out, but I'll post one of the solutions listed.
One of the Solutions posted on that forum is this:
//get the image pixel
int imgPixel = image.getRGB(x,y);
//get the mask pixel
int maskPixel = mask.getRGB(x,y);
//now, get rid of everything but the blue channel
//and shift the blue channel into the alpha channels sample space.
maskPixel = (maskPixel &0xFF)<<24
//now, merge img and mask pixels and copy them back to the image
image.setRGB(x,y,imgPixel|maskPixel);

I found a solution to my problem i solved my problem by tinting my bitmap using PorterDuffColorFilter in a following way.
public Bitmap tintBitmap(Bitmap bitmap, int color) {
Paint paint = new Paint();
paint.setColorFilter(new PorterDuffColorFilter(color, PorterDuff.Mode.SRC_IN));
Bitmap bitmapResult = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmapResult);
canvas.drawBitmap(bitmap, 0, 0, paint);
return bitmapResult;
}

Android Canvas matrix

For a school project I need to make a module to shrink a bitmap. So I made a matrix for this but when I draw directly the bitmap with the matrix like this :
canvas.drawBitmap(Bmp, ShrinkMatrice, p);
This work very fine, but I need to assign this matrix into the Bmp so I used a second canvas like this :
Canvas SuperCanvas = new Canvas(Bmp);
SuperCanvas.drawBitmap(Bmp, ShrinkMatrice, p);
but when I look the result with this :
canvas.drawBitmap(Bmp, 0,0, p);
the result look like this ( see the picture on the link ), the rest of the page is not draw correctly ...
if someone can explain me this problem :/...
Thank you in advance...
(Sorry if I made some error it's my first time on stackoverflow )

OutOfMemoryError: Android large Bitmap rotation (90°)

I have a big Memory Problem:
// in sourceImage is a big JPEG previously loaded
Matrix mat = new Matrix();
mat.postRotate(90);
Bitmap rotatedImage = Bitmap.createBitmap(sourceImage, 0, 0, sourceImage.getWidth(), sourceImage.getHeight(), mat, true);
Always i Run this code, my App crashes and says "VM won't let us allocate xxxxxx bytes"
Can you help me?
Edit:
I saw much similar questions here, but i don't know how to recycle the sourceImage before rotatating it... (cause the second instance is to big to hold it at the same time)
Thanks.

You can't create a new rotated bitmap without holding temporary 2 bitmaps in memory.
But you can display the bitmap rotated without creating a new bitmap (apply a transformation).
ImageView does not come with rotation capabilities, so you should write your own extended version of ImageView (RotatedImageView?).
The idea is to override the onDraw method with something like this (not tested).
#Override
public void onDraw(Canvas canvas) {
canvas.rotate((int)(angle * 180 / Math.PI), getWidth() >> 1, getHeight() >> 1);
super.onDraw(canvas);
}

For others like me:
there's an option to have the camera perform the rotation,
https://stackoverflow.com/a/16010289/755804

Android: Canvas made out of multiple images won't save

Right my title isn't the best in the world. I've got a big code that's supposed to make on big bitmap out of multiple bitmaps. I've isolated the problem to this part of the code
bity = Bitmap.createBitmap(specialWidth,specialHeight,Bitmap.Config.ALPHA_8);
Canvas canvas = new Canvas(bity);
float left=0.0f;
for (int i = 0; i < imagesArrayz.length; i++){
float top=0.0f;
canvas.drawBitmap(imagesArrayz[i], left, top, null);
left+=imagesArrayz[i].getWidth();
}
To explain: "bity" is a globally defined Bitmap object and it's unassigned untill this point; imagesArrayz is an array of 5 Bitmaps that has already ben assigned and has ben assigned correctly (i tested it to see if each image is in the array)
After this i just have a function that saves the global variable bity to a file. THE PROBLEM is that instaid of saving my nicely drawn canvas it saves an empty jpg file of 0kb. Please help!

I answered my own question... Replace ALPHA_8 with ARGB_8888 and it all magically works.
Someone shoot me please...

placeing bitmaps in live wallpapers

Hello I am trying to place acouple bitmaps on the screen and rotate them. I can get this to work by doing
canvas.drawBitmap(pic2, rotatePic, null);
rotatePic is matrix with
postRotate(5, pic2.getHieght()/2, pic2.getWidth()/2)
this rotates the pic and puts it at 0, 0 so to place it i tried
Bitmap topPic = Bitmap.createBitmap(pic2, 0, 0, pic2.getWidth(),
pic2.getHeight(), rotatePic, false);
than place with
canvas.drawBitmap(topPic, 200, 100, null);
it places it correctley but it no longer rotates correctley it looks like it is bouncing and spinning I've tried everthing

You can alternatively try rotating the canvas itself, using
canvas.rotate(degress, px, py);
Here's a link to the Android reference page for this:
Canvas.rotate();
Hope this helps!!