[SOLVED] Screen capture with alpha background

Ali_RS · January 30, 2021, 10:59am

Yeah, JME will drop alpha when writing image, see

jMonkeyEngine/jmonkeyengine/blob/a79be13ac83fdf421e00e6ca0c189d8f361b00d7/jme3-desktop/src/main/java/com/jme3/system/JmeDesktopSystem.java#L93


      
              Graphics2D g2d = awtImage.createGraphics();
              g2d.setRenderingHint(RenderingHints.KEY_RENDERING,
                                   RenderingHints.VALUE_RENDER_SPEED);
              g2d.drawImage(original, transformOp, 0, 0);
              g2d.dispose();
              return awtImage;
          }
          
          @Override
          public void writeImageFile(OutputStream outStream, String format, ByteBuffer imageData, int width, int height) throws IOException {
              BufferedImage awtImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
              Screenshots.convertScreenShot2(imageData.asIntBuffer(), 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);
              }

For detailed info, please see this topic

I ended up rendering scene to a back buffer and using this utility class to export PNGs.

github.com

NemesisMate/util-jme3/blob/c7958446898adeffad74af3aa0eb9f0a35738085/util-jme3-base/src/main/java/com/nx/util/jme3/base/ImageUtil.java#L22


      
          import java.awt.image.BufferedImage;
          import java.io.File;
          import java.io.FileOutputStream;
          import java.io.IOException;
          import java.nio.ByteBuffer;
          import java.util.ArrayList;
          
          /**
           * Created by NemesisMate on 13/03/17.
           */
          public final class ImageUtil {
          
              private static final Logger log = LoggerFactory.getLogger(ImageUtil.class);
          
              private ImageUtil() {
          
              }
          
              public static Image createEmptyImage(int size) {
                  return createEmptyImage(size, true);
              }