1 files changed, 106 insertions, 0 deletions
diff --git a/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java b/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java
new file mode 100644
index 0000000000..bf85a767c2
--- /dev/null
+++ b/platform_tools/android/apps/skar_java/src/main/java/com/google/ar/core/examples/java/helloskar/DrawManager.java
@@ -0,0 +1,106 @@
+package com.google.ar.core.examples.java.helloskar;
+
+import android.graphics.Canvas;
+import android.graphics.ColorFilter;
+import android.graphics.Paint;
+import android.graphics.RectF;
+
+import com.google.skar.SkARMatrix;
+import com.google.skar.SkARUtil;
+
+import java.util.ArrayList;
+
+public class DrawManager {
+    private float[] projectionMatrix = new float[16];
+    private float[] viewMatrix = new float[16];
+    private float[] viewportMatrix = new float[16];
+    private ColorFilter lightFilter;
+    public ArrayList<float[]> modelMatrices = new ArrayList<>();
+
+    public void updateViewportMatrix(float width, float height) {
+        viewportMatrix = SkARMatrix.createViewportMatrix(width, height);
+    }
+
+    public void updateProjectionMatrix(float[] projectionMatrix) {
+        this.projectionMatrix = projectionMatrix;
+    }
+
+    public void updateViewMatrix(float[] viewMatrix) {
+        this.viewMatrix = viewMatrix;
+    }
+
+    public void updateLightColorFilter(float[] colorCorr) {
+        lightFilter = SkARUtil.createLightCorrectionColorFilter(colorCorr);
+    }
+
+    public void drawCircle(Canvas canvas) {
+        if (modelMatrices.isEmpty()) {
+            return;
+        }
+        Paint p = new Paint();
+        p.setColorFilter(lightFilter);
+        p.setARGB(180, 100, 0, 0);
+
+        canvas.save();
+        canvas.setMatrix(SkARMatrix.createPerspectiveMatrix(modelMatrices.get(0),
+                viewMatrix, projectionMatrix, viewportMatrix));
+        canvas.drawCircle(0, 0, 0.1f, p);
+        canvas.restore();
+    }
+
+    public void drawRect(Canvas canvas) {
+        if (modelMatrices.isEmpty()) {
+            return;
+        }
+        Paint p = new Paint();
+        p.setColorFilter(lightFilter);
+        p.setARGB(180, 0, 0, 255);
+        canvas.save();
+        canvas.setMatrix(SkARMatrix.createPerspectiveMatrix(modelMatrices.get(0),
+                viewMatrix, projectionMatrix, viewportMatrix));
+        RectF rect = new RectF(0, 0, 0.2f, 0.2f);
+        canvas.drawRect(rect, p);
+        canvas.restore();
+    }
+
+    public void drawText(Canvas canvas, String text) {
+        if (modelMatrices.isEmpty()) {
+            return;
+        }
+        Paint p = new Paint();
+        float textSize = 100;
+        p.setColorFilter(lightFilter);
+        p.setARGB(255, 0, 255, 0);
+        p.setTextSize(textSize);
+
+
+        float[] scaleMatrix = getTextScaleMatrix(textSize);
+        float[] rotateMatrix = createXYtoXZRotationMatrix();
+        float[] actualModel = new float[16];
+        android.opengl.Matrix.setIdentityM(actualModel, 0);
+
+        android.opengl.Matrix.multiplyMM(actualModel, 0, scaleMatrix, 0, rotateMatrix, 0);
+        android.opengl.Matrix.multiplyMM(actualModel, 0, modelMatrices.get(0), 0, actualModel, 0);
+
+        canvas.save();
+        canvas.setMatrix(SkARMatrix.createPerspectiveMatrix(actualModel,
+                viewMatrix, projectionMatrix, viewportMatrix, false));
+        canvas.drawText(text, 0, 0, p);
+        canvas.restore();
+    }
+
+    private float[] getTextScaleMatrix(float size) {
+        float scaleFactor = 1 / (size * 10);
+        float[] initScale = new float[16];
+        android.opengl.Matrix.setIdentityM(initScale, 0);
+        android.opengl.Matrix.scaleM(initScale, 0, scaleFactor, scaleFactor, scaleFactor);
+        return initScale;
+    }
+
+    private float[] createXYtoXZRotationMatrix() {
+        float[] skiaRotation = new float[16];
+        android.opengl.Matrix.setIdentityM(skiaRotation, 0);
+        android.opengl.Matrix.rotateM(skiaRotation, 0, 90, 1, 0, 0);
+        return skiaRotation;
+    }
+}