AlphaScaleShaderProgram.java
/*
* Copyright 2022 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.media3.effect;
import android.content.Context;
import android.opengl.GLES20;
import androidx.media3.common.VideoFrameProcessingException;
import androidx.media3.common.util.GlProgram;
import androidx.media3.common.util.GlUtil;
import androidx.media3.common.util.Size;
import java.io.IOException;
/** Scales the alpha value for each pixel in the fragment shader. */
/* package */ final class AlphaScaleShaderProgram extends SingleFrameGlShaderProgram {
private static final String VERTEX_SHADER_PATH = "shaders/vertex_shader_transformation_es2.glsl";
private static final String FRAGMENT_SHADER_PATH = "shaders/fragment_shader_alpha_scale_es2.glsl";
private final GlProgram glProgram;
/**
* Creates a new instance.
*
* @param context The {@link Context}.
* @param useHdr Whether input textures come from an HDR source. If {@code true}, colors will be
* in linear RGB BT.2020. If {@code false}, colors will be in linear RGB BT.709.
* @param alphaScale The alpha scale factor.
* @throws VideoFrameProcessingException If a problem occurs while reading shader files.
*/
public AlphaScaleShaderProgram(Context context, boolean useHdr, float alphaScale)
throws VideoFrameProcessingException {
super(/* useHighPrecisionColorComponents= */ useHdr);
try {
glProgram = new GlProgram(context, VERTEX_SHADER_PATH, FRAGMENT_SHADER_PATH);
} catch (IOException | GlUtil.GlException e) {
throw new VideoFrameProcessingException(e);
}
// Draw the frame on the entire normalized device coordinate space, from -1 to 1, for x and y.
glProgram.setBufferAttribute(
"aFramePosition",
GlUtil.getNormalizedCoordinateBounds(),
GlUtil.HOMOGENEOUS_COORDINATE_VECTOR_SIZE);
float[] identityMatrix = GlUtil.create4x4IdentityMatrix();
glProgram.setFloatsUniform("uTransformationMatrix", identityMatrix);
glProgram.setFloatsUniform("uTexTransformationMatrix", identityMatrix);
glProgram.setFloatUniform("uAlphaScale", alphaScale);
}
@Override
public Size configure(int inputWidth, int inputHeight) {
return new Size(inputWidth, inputHeight);
}
@Override
public void drawFrame(int inputTexId, long presentationTimeUs)
throws VideoFrameProcessingException {
try {
glProgram.use();
glProgram.setSamplerTexIdUniform("uTexSampler", inputTexId, /* texUnitIndex= */ 0);
glProgram.bindAttributesAndUniforms();
// The four-vertex triangle strip forms a quad.
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, /* first= */ 0, /* count= */ 4);
} catch (GlUtil.GlException e) {
throw new VideoFrameProcessingException(e, presentationTimeUs);
}
}
}