Fix PNG transparency (Fixes #2)

src/main/scala/edu/stanford/graphics/shapenet/jme3/viewer/JmeSystemMod.java

@@ -0,0 +1,82 @@
+package edu.stanford.graphics.shapenet.jme3.viewer;
+
+import com.jme3.util.Screenshots;
+
+import javax.imageio.IIOImage;
+import javax.imageio.ImageIO;
+import javax.imageio.ImageWriteParam;
+import javax.imageio.ImageWriter;
+import javax.imageio.plugins.jpeg.JPEGImageWriteParam;
+import javax.imageio.stream.ImageOutputStream;
+import javax.imageio.stream.MemoryCacheImageOutputStream;
+import java.awt.*;
+import java.awt.geom.AffineTransform;
+import java.awt.image.AffineTransformOp;
+import java.awt.image.BufferedImage;
+import java.awt.image.DataBufferInt;
+import java.awt.image.WritableRaster;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.ByteBuffer;
+
+public final class JmeSystemMod {
+
+    private static void fixAlphaAndSwapChannels(BufferedImage img) {
+        final WritableRaster wr = img.getRaster();
+        final DataBufferInt db = (DataBufferInt)wr.getDataBuffer();
+        final int[] cpuArray = db.getData();
+        for (int i = 0; i < cpuArray.length; i++) {
+            int p = cpuArray[i];
+            // Fix alpha channel (set to 0 for complete transparency)
+            if (p == -1) {
+                p &= 0x00ffffff;
+            } else {
+                // Convert ABGR to ARGB
+                final int b = p >> 16 & 0xff;
+                final int r = p & 0xff;
+                p = (p & 0xff00ff00) | r << 16 | b;
+            }
+            cpuArray[i] = p;
+        }
+    }
+
+    private static BufferedImage verticalFlip(BufferedImage original) {
+        AffineTransform tx = AffineTransform.getScaleInstance(1, -1);
+        tx.translate(0, -original.getHeight());
+        AffineTransformOp transformOp = new AffineTransformOp(tx, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
+        BufferedImage awtImage = new BufferedImage(original.getWidth(), original.getHeight(), BufferedImage.TYPE_INT_ARGB);
+        Graphics2D g2d = awtImage.createGraphics();
+        g2d.setRenderingHint(RenderingHints.KEY_RENDERING,
+                RenderingHints.VALUE_RENDER_SPEED);
+        g2d.drawImage(original, transformOp, 0, 0);
+        g2d.dispose();
+        return awtImage;
+    }
+
+    public static void writeImageFile(OutputStream outStream, String format, ByteBuffer imageData, int width, int height) throws IOException {
+        BufferedImage awtImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
+        Screenshots.convertScreenShot2(imageData.asIntBuffer(), awtImage);
+        fixAlphaAndSwapChannels(awtImage);
+
+        ImageWriter writer = ImageIO.getImageWritersByFormatName(format).next();
+        ImageWriteParam writeParam = writer.getDefaultWriteParam();
+
+        if (format.equals("jpg")) {
+            JPEGImageWriteParam jpegParam = (JPEGImageWriteParam) writeParam;
+            jpegParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
+            jpegParam.setCompressionQuality(0.95f);
+        }
+
+        awtImage = verticalFlip(awtImage);
+
+        ImageOutputStream imgOut = new MemoryCacheImageOutputStream(outStream);
+        writer.setOutput(imgOut);
+        IIOImage outputImage = new IIOImage(awtImage, null, null);
+        try {
+            writer.write(null, outputImage, writeParam);
+        } finally {
+            imgOut.close();
+            writer.dispose();
+        }
+    }
+}

src/main/scala/edu/stanford/graphics/shapenet/jme3/viewer/OffscreenView.scala

@@ -89,7 +89,7 @@ class OffscreenView(val renderManager: RenderManager,
     logger.info("Saving offscreen view to: {0}", file.getAbsolutePath())
     try {
       outStream = IOUtils.fileOutputStream(filename)
-      JmeSystem.writeImageFile(outStream, imageFormat, outBuf, width, height)
+      JmeSystemMod.writeImageFile(outStream, imageFormat, outBuf, width, height)
     } catch {
       case ex: IOException => {
         logger.error("Error while saving offscreen view", ex)

src/main/scala/edu/stanford/graphics/shapenet/jme3/viewer/ScreenshotAppState.java

@@ -201,7 +201,7 @@ public void postFrame(FrameBuffer out) {
       OutputStream outStream = null;
       try {
         outStream = new FileOutputStream(file);
-        JmeSystem.writeImageFile(outStream, imageFormat, outBuf, width, height);
+        JmeSystemMod.writeImageFile(outStream, imageFormat, outBuf, width, height);
         logger.log(Level.INFO, "Saved ScreenShot to: " + file.getAbsolutePath());
       } catch (IOException ex) {
         logger.log(Level.SEVERE, "Error while saving screenshot", ex);