Develop Reference

How to draw an image on top a bitmap and combine as one bitmap in Android Java

I am developing an Android application using Java. I am doing some image manipulating in my application. First of all, I like to save I have no knowledge about image processing. But, I am trying to get into it. What I would like to do now is draw a simple image on a bitmap and save it as one bitmap.
I am loading an image from asset folder as a bitmap like this.
Bitmap rectBitmap = BitmapFactory.decodeStream(istr);
Let's say the photo is a just simple rectangle like this.
Then I would like to draw a bitmap (triangle shape) using coordinates point. The image would be some this.
My imagination of code would be like this.
rectBitmap.drawOnTop(coorPointOneValues, coorPointTwoValues, coorPointThreeValues);
Coordinate point values would be x and y value since I am working on the 2D coordinate system.
Then I would like to save the image something like this after drawing traingle
rectBitmap = rectBitmap.saveBitmap();
How can I do it? The scenario mentioned is a possible way that I can think of. If it is not possible, what would be the other way around?

You can do it like this.
1, read or create your bitmap:
Bitmap rectBitmap = BitmapFactory.decodeStream(istr);
Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
2, create a canvas on the bitmap:
Canvas canvas = new Canvas(bitmap);
3, draw something:
canvas.drawColor(Color.RED)
canvas.drawRect / canvas.drawLine / canvas.drawArc ...
//for triangle shape you can use drawPath
4, save the bitmap:
bitmap.compress(CompressFormat format, int quality, OutputStream stream)

how to crop top,left,right and bottom portion of imageview in android

In my application i am getting transparent pixels in my Imageview while taking screenshot.How to cut top,left,right and bottom portion of Imageview.I tried below code but not working
Bitmap bitmap = Bitmap.createBitmap(imgView.getWidth(),imgView.getHeight(), Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
imgView.draw(canvas);
Bitmap result =Bitmap.createBitmap(bitmap,imgView.getLeft()+10, imgView.getTop()+50, imgView.getWidth()-20, imgView.getHeight()-100);
bitmap.recycle();
please help me to solve this issue.

I am not very sure what are you referring with "not working", but from first sight I would suggest you to change from
Bitmap result =Bitmap.createBitmap(bitmap,imgView.getLeft()+10, imgView.getTop()+50, imgView.getWidth()-20, imgView.getHeight()-100);
to
Bitmap result =Bitmap.createBitmap(bitmap, 10, 50, bitmap.getWidth()-20, bitmap.getHeight()-100);
But I would not recommend you to use this kind of approach which explicitly setting width and height value.

create a bitmap with a bitmap inside

I know - the title may sounds strange. Let me explain:
I created an image to show you, what I'm talking about:
I got an image (Bitmap (1)), that as the size of 150w/200h.
Now I need to make the bitmap bigger ((2) 400w/400h), but the original image must have the same size. So that the image is embedded in white background.
I think one way to solve it is this:
* create a big bitmap
* create a canvas for it
* draw the original bitmap on the canvas
* draw the canvas
* generate a bitmap of the canvas
The problem for me is, that it must be done in a background thread without drawing a view.
I hope you understand me.

You can use the code bellow to achive it. Where smallBitmap is your original image and bigBitmap is the final image:
Bitmap bigBitmap = Bitmap.createBitmap(width, height , Bitmap.Config.ARGB_8888);
canvas = new Canvas(bigBitmap);
canvas.drawBitmap(smallBitmap, left, top, new Paint());
Regards.

This should do the trick.
Create a thread and in that thread object:
Create a new bitmap.
Create a canvas based on that bitmap.
Draw your bitmap to that canvas
and voila!
I hope this helps.

How to change black background color of bitmap to transparent?

I am creating Bitmap using following code:
Bitmap bm= Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
But I want to change Background color from black to transparent because I want to use this object in another Activity also. I searched a lot but I am unable to find solution.
Please help.
Thanks in advance.

Of course the Bitmap created in mode ARGB_8888 supports transparency
But the alpha channel is initially filled by 0xff, so bitmap is opaque.
You have to clear the whole bitmap including the alpha channel like this:
Canvas c = new Canvas(bm);
c.drawColor(0, Mode.CLEAR);

Bitmap images do not support transparency. You should use a GIF or a PNG.
http://www.gimpchat.com/viewtopic.php?f=8&t=1290

Android: how to simply draw a bitmap on another bitmap

I'm new to Android dev and I'm having a hard time trying to do something which seems obvious to me: drawing little images on top of a bigger image.
Let's say that I have a 500x500 image and I want to draw icons at different locations. Icons are png files that I load with:
Bitmap img =
BitmapFactory.decodeResource(getResources(),
R.drawable.idIcon1)
My "background image" is a LayerDrawable.
Then, I am totally lost... Do I have to create a canvas ? How to draw on my "background image" my icons at different positions?

int positionLeft=0;
int positionTop=0;
Bitmap newBitmap =Bitmap.createBitmap(backgroundBitmap.getWidth(),bitmap.getHeight(),Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(newBitmap);
canvas.drawBitmap(backgroundBitmap, positionLeft, positionTop,null);
positionLeft=100;
positionTop=100;
canvas.drawBitmap(iconBitmap,positionLeft,positionTop,null);
imageView.setImageBitmap(newBitmap);

You're making simple things difficult. Just use a layout with android:background attribute, and then add ImageViews dynamically with the necessary bitmaps inside.