CODEWITHSUNDEEP
javaandroidopengl-esgrafika
natario
natario

Reputation: 25204

Scaling and rotating texture transformation Matrix at the same time

Starting from grafika examples I am trying to capture a camera stream to file. Before encoding I need to apply some transformations:

  1. Rotate the image

I can do this:

Matrix.translateM(transform, 0, 0.5F, 0.5F, 0);
Matrix.rotateM(transform, 0, rotation, 0, 0, 1);
Matrix.translateM(transform, 0, -0.5F, -0.5F, 0);
  1. Apply a scale and a translation

The image comes in compressed along one axis. So I have to scale along that axis, than translate a bit so that we see the middle part. Again, I can do this as follows:

float scaleX = mScaleX; // < 1 or == 1
float scaleY = mScaleY; // < 1 or == 1
float scaleTranslX = (1F - scaleX) / 2F;
float scaleTranslY = (1F - scaleY) / 2F;
Matrix.translateM(transform, 0, scaleTranslX, scaleTranslY, 0);
Matrix.scaleM(transform, 0, scaleX, scaleY, 1);

The translation is to obtain a 'center crop' in the final result, as the encoder will only capture what's drawn in the given viewport.

However, I am lost at combining the two operations together. I have spent a few hours on this and what I have researched did not help. Can anyone figure this out?

Upvotes: 3

Views: 456

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