Android - Correspondence between ImageView coordinates and Bitmap Pixels
- by Matteo
In my application I want the user to be able to select some content of an Image contained inside an ImageView.
To select the content I subclassed the ImageView class making it implement the OnTouchListener so to draw over it a rectangle with borders decided by the user.
Here is an example of the result of the drawing (to have an idea you can think of it as when you click with the mouse on your desktop and drag the mouse):
Now I need to determine which pixels of the Bitmap image correspond to the selected part. It's kind of easy to determine which are the points of the ImageView belonging to the rectangle, but I don't know how to get the correspondent pixels, since the ImageView has a different aspect ratio than the original image.
I followed the approach described especially here, but also here, but am not fully satisfied because in my opinion the correspondence made is 1 on 1 between pixels and points on the ImageView and does not give me all the correspondent pixels on the original image to the selected area.
Calling hoveredRect the rectangle on the ImageView the points inside of it are:
class Point {
float x, y;
@Override
public String toString() {
return x + ", " + y;
}
}
Vector<Point> pointsInRect = new Vector<Point>();
for( int x = hoveredRect.left; x <= hoveredRect.right; x++ ){
for( int y = hoveredRect.top; y <= hoveredRect.bottom; y++ ){
Point pointInRect = new Point();
pointInRect.x = x;
pointInRect.y = y;
pointsInRect.add(pointInRect);
}
}
How can I obtain a Vector<Pixels> pixelsInImage containing the correspondent pixels?
