CODEWITHSUNDEEP
androidopengl-es
chohyunwook
chohyunwook

Reputation: 401

use OpenGL draw text on android

I want draw square and draw Text on GLSurfaceView camera preview.

first I try draw square

private void drawSquare() {
    GLES20.glEnable(GLES20.GL_SCISSOR_TEST);
    GLES20.glScissor(20, 300, 500, 50);
    GLES20.glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
    GLES20.glDisable(GLES20.GL_SCISSOR_TEST);
}

this method call on onDrawFrame(); and show square on camera preview glsurfaceview.

and I try draw Text 

public void GLText(GL10 gl) {

    Bitmap bitmap = Bitmap.createBitmap(64, 64, Bitmap.Config.ARGB_4444);
    Canvas canvas = new Canvas(bitmap);
    bitmap.eraseColor(0);

    Paint paint = new Paint();
    paint.setTextSize(18);
    paint.setAntiAlias(true);
    paint.setARGB(0xff, 0xff, 0xff, 0xff);
    paint.setTextAlign(Paint.Align.LEFT);
    paint.setTextScaleX(0.5f);
    canvas.drawText("testGLText", 0.f, 15.f, paint);

    GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);

    bitmap.recycle();
}

and show text. but backgroud color green

enter image description here

why background color green? please help for me.

thanks.

Upvotes: 1

Views: 1198

Answers (1)

Sung
Sung

Reputation: 1066

I don't see your code drawing texts using openGL api but there is no reason to set your fbo green. 

    GLES20.glEnable(GLES20.GL_SCISSOR_TEST);
    GLES20.glScissor(20, 300, 500, 50);
    GLES20.glClearColor(1.0f, 0.0f, 0.0f, 1.0f); // here you initialize your fbo color as black
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
    GLES20.glDisable(GLES20.GL_SCISSOR_TEST);

If you want to draw a square, follow these steps below.

glclearcolor(...); //Actually, glclearColor() and glclear() are not required.
glclear();
glviewport(....);
gluseprogram() // a shader program you compiled 
bindVBO() // VBO you already set in this case, it saves four vertices
glactivetexture() and bindtexture()
gluniform1f(..) // for the texture
gldrawarray(...) or gldrawelement(...)

Upvotes: 1

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