How To Render Text To Bitmap And Draw It

I am new to android, and my group is currently creating a graphing application using a GlSurfaceView using opengl es 2.0. We have recently displayed the grid and tickmarks on the p

Solution 1:

You're asking a lot of questions, but I'll try to answer a few:

• so how large should my bitmap be?

  It's really up to you, depending on how crisp you want the text to be. You could allocate a huge bitmap with hundreds of pixels for each character that would zoom very well, or a very small bitmap with limited resolution. I'd say whatever "font size" you want to have, allocate at least that many pixels in height for each character. So if you want to draw something with a font size of "20", then maybe you need a bitmap 5x20 by 3x20 or 100x60.

• How would I draw single digit numbers from the bit map?

  You'll draw a quad with opengl in the place where you want to draw a letter, and you use the texture coordinates of that quad to pick a letter.

  For example if I want to draw an X, then you draw a quad on the screen, and assign it's texcoords from (0,0) to (0.2, 0.33), which selects the left 1/5th of the texture, and the bottom 1/3rd of the texture. You'll see how a box like this lines up with the position of the "X" in your texture.

• How would I draw numbers with more than one digit?

  You just draw two independent single digits right next to each other.

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If your only goal here is to draw text in Android, it might be easier to just use a FrameLayout, and layer TextViews overtop of your GLSurfaceView. OpenGL isn't designed for text which makes it somewhat cumbersome.