I wrote opengl android code to show a bitmap on a square. But bitmap was drawn in reverse. When i change texture array combination to the commented code it is drawn correctly. But i insist my texture array must be as below . Am i thinking wrong ?
/** The initial vertex definition */ private float vertices[] = { -1.0f, 1.0f, 0.0f, //Top Left -1.0f, -1.0f, 0.0f, //Bottom Left 1.0f, -1.0f, 0.0f, //Bottom Right 1.0f, 1.0f, 0.0f //Top Right }; /** Our texture pointer */ private int[] textures = new int[1]; /** The initial te开发者_运维技巧xture coordinates (u, v) */ private float texture[] = { //Mapping coordinates for the vertices // 1.0f, 0.0f, // 1.0f, 1.0f, // 0.0f, 1.0f, // 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, }; /** The initial indices definition */ private byte indices[] = { //2 triangles 0,1,2, 2,3,0, };
Whereas Android uses the top-left corner as being 0,0 of the coordinate system, OpenGL uses the bottom-left corner being 0,0 which is why your texture gets flipped.
A common solution to this is to flip your texture at load time,
Matrix flip = new Matrix();
flip.postScale(1f, -1f);
Bitmap bmp = Bitmap.createBitmap(resource, 0, 0, resource.getWidth(), resource.getHeight(), flip, true);
Actually, I think Will Kru's solution should have flipped the background around both axes
flip.postScale(-1f, -1f);
That solution worked for me!
This worked for me. (no need to create another bitmap and scale)
private float vertices[] = {
1.0f, -1.0f, 0.0f, //Bottom Right
1.0f, 1.0f, 0.0f, //Top Right
-1.0f, 1.0f, 0.0f, //Top Left
-1.0f, -1.0f, 0.0f, //Bottom Left
};
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