Skip to main content

draw rectangle on a picture from pixels coordinates



with the following code i can draw a rectangle on my bitmap image.







Paint paint = new Paint();

paint.setStyle(Style.STROKE);

paint.setColor(Color.BLUE);

publishProgress(80);

Canvas canvas = new Canvas(mBitmap);

publishProgress(85);

canvas.drawRect(200, 100, 200, 100, paint);

bitmap.recycle();

channel.close();







i've read that the values given in canvas.drawRect(200, 100, 200, 100, paint); represent respectively left x, top y, right x and bottom y. So my questions are :





  • are those values in pixels? ppi or what??







  • how can i draw a rectangle on my image if i have only the coordinates of each corners in pixels as shown on the picture below ? assuming that i have A (x, y) B (x, y), C(x, y) and D(x, y) with x and y expressed in pixels from the axes of the picture below. NB: i don't have control on A,B,C,D they are given to me from a web service





    rectangle i want to draw






Comments

  1. I don't think you have a problem here, you would just do this:

    canvas.drawRect(a.getX(), a.getY(), c.getX(), c.getY(), paint);

    Yes the values are in pixels however your origin (0,0) is the top left of the canvas normally. Y value becomes more positive as you move down the canvas.

    ReplyDelete

Post a Comment

Popular posts from this blog

Slow Android emulator

I have a 2.67 GHz Celeron processor, 1.21 GB of RAM on a x86 Windows XP Professional machine. My understanding is that the Android emulator should start fairly quickly on such a machine, but for me it does not. I have followed all instructions in setting up the IDE, SDKs, JDKs and such and have had some success in staring the emulator quickly but is very particulary. How can I, if possible, fix this problem?