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| -rw-r--r-- | graphics/java/android/graphics/SurfaceTexture.java | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/graphics/java/android/graphics/SurfaceTexture.java b/graphics/java/android/graphics/SurfaceTexture.java index 4c659d4..1fc2722 100644 --- a/graphics/java/android/graphics/SurfaceTexture.java +++ b/graphics/java/android/graphics/SurfaceTexture.java @@ -32,6 +32,17 @@ import android.os.Message; * updated to contain the most recent image from the image stream. This may cause some frames of * the stream to be skipped. * + * <p>When sampling from the texture one should first transform the texture coordinates using the + * matrix queried via {@link #getTransformMatrix}. The transform matrix may change each time {@link + * #updateTexImage} is called, so it should be re-queried each time the texture image is updated. + * This matrix transforms traditional 2D OpenGL ES texture coordinate column vectors of the form (s, + * t, 0, 1) where s and t are on the inclusive interval [0, 1] to the proper sampling location in + * the streamed texture. This transform compensates for any properties of the image stream source + * that cause it to appear different from a traditional OpenGL ES texture. For example, sampling + * from the bottom left corner of the image can be accomplished by transforming the column vector + * (0, 0, 0, 1) using the queried matrix, while sampling from the top right corner of the image can + * be done by transforming (1, 1, 0, 1). + * * <p>The texture object uses the GL_TEXTURE_EXTERNAL_OES texture target, which is defined by the * OES_EGL_image_external OpenGL ES extension. This limits how the texture may be used. * |