Add Halftone filter

Author: ryohey

library/src/jp/co/cyberagent/android/gpuimage/GPUImageHalftoneFilter.java

@@ -0,0 +1,67 @@
+package jp.co.cyberagent.android.gpuimage;
+
+import android.opengl.GLES20;
+
+public class GPUImageHalftoneFilter extends GPUImageFilter {
+    public static final String HALFTONE_FRAGMENT_SHADER = "" +
+            "varying highp vec2 textureCoordinate;\n" +
+
+            "uniform sampler2D inputImageTexture;\n" +
+
+            "uniform highp float fractionalWidthOfPixel;\n" +
+            "uniform highp float aspectRatio;\n" +
+
+            "const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);\n" +
+
+            "void main()\n" +
+            "{\n" +
+            "  highp vec2 sampleDivisor = vec2(fractionalWidthOfPixel, fractionalWidthOfPixel / aspectRatio);\n" +
+            "  highp vec2 samplePos = textureCoordinate - mod(textureCoordinate, sampleDivisor) + 0.5 * sampleDivisor;\n" +
+            "  highp vec2 textureCoordinateToUse = vec2(textureCoordinate.x, (textureCoordinate.y * aspectRatio + 0.5 - 0.5 * aspectRatio));\n" +
+            "  highp vec2 adjustedSamplePos = vec2(samplePos.x, (samplePos.y * aspectRatio + 0.5 - 0.5 * aspectRatio));\n" +
+            "  highp float distanceFromSamplePoint = distance(adjustedSamplePos, textureCoordinateToUse);\n" +
+            "  lowp vec3 sampledColor = texture2D(inputImageTexture, samplePos).rgb;\n" +
+            "  highp float dotScaling = 1.0 - dot(sampledColor, W);\n" +
+            "  lowp float checkForPresenceWithinDot = 1.0 - step(distanceFromSamplePoint, (fractionalWidthOfPixel * 0.5) * dotScaling);\n" +
+            "  gl_FragColor = vec4(vec3(checkForPresenceWithinDot), 1.0);\n" +
+            "}";
+
+    private int mFractionalWidthOfPixelLocation;
+    private int mAspectRatioLocation;
+
+    private float mFractionalWidthOfAPixel;
+    private float mAspectRatio;
+
+    public GPUImageHalftoneFilter() {
+        this(0.01f);
+    }
+
+    public GPUImageHalftoneFilter(float fractionalWidthOfAPixel) {
+        super(NO_FILTER_VERTEX_SHADER, HALFTONE_FRAGMENT_SHADER);
+        mFractionalWidthOfAPixel = fractionalWidthOfAPixel;
+    }
+
+    @Override
+    public void onInit() {
+        super.onInit();
+        mFractionalWidthOfPixelLocation = GLES20.glGetUniformLocation(getProgram(), "fractionalWidthOfPixel");
+        mAspectRatioLocation = GLES20.glGetUniformLocation(getProgram(), "aspectRatio");
+        setFractionalWidthOfAPixel(mFractionalWidthOfAPixel);
+    }
+
+    @Override
+    public void onOutputSizeChanged(final int width, final int height) {
+        super.onOutputSizeChanged(width, height);
+        setAspectRatio((float)height / (float) width);
+    }
+
+    public void setFractionalWidthOfAPixel(final float fractionalWidthOfAPixel) {
+        mFractionalWidthOfAPixel = fractionalWidthOfAPixel;
+        setFloat(mFractionalWidthOfPixelLocation, mFractionalWidthOfAPixel);
+    }
+
+    public void setAspectRatio(final float aspectRatio) {
+        mAspectRatio = aspectRatio;
+        setFloat(mAspectRatioLocation, mAspectRatio);
+    }
+}