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javaandroidandroid-imageviewscaleandroid-canvas

Calculate new point coordinates after imageview translation

I need help calculating new coordinates after an imageview translation.

I am working on an android app that will plot points on a map.

The map is downloaded from a backed service.

The points I need to plot come from the backend, and their positions are relative to the map size (8000w x 4450h).

The app (using glide) sets the image in a custom imageview. When that happens, the map is scaled down to fit the screen.

viewH = 735.

viewW = 1080.

I then need to plot the locations; however, the plotted coordinates need to be translated to match the new scale.

Here is how I am calculating it now...which gets the points in the correct area...but they are not precise (plotting to low on y axis):

newX = oldX / (originalMapHeight / imageviewHeight).

newY = oldY / (originalMapWidth / imageviewWidth).

Can someone help me get a more accurate translation of the x,y coordinates? I cannot find anything regarding this, but it may be due to me not knowing what exactly to search.

Thanks!

Solution

  • You can use min-max normalization for this. The formula is enter image description here

    For your case, the formula reduces to

    NewX = (oldX * imageViewWidth) / originalMapWidth

    NewY = (oldY * imageViewHeight) / originalMapHeight