使用Apache POI將幻燈片轉換為圖像時，ppt背景為黑色

Question

我正在使用下面的代碼將ppt幻燈片轉換為圖像。

BufferedImage imBuff = new BufferedImage(pgsize.width, (pgsize.height) * slides.size(), BufferedImage.TYPE_INT_RGB);
Graphics g = imBuff.getGraphics();
Graphics2D graphics = img.createGraphics();
graphics.setRenderingHint(Drawable.FONT_MAP, fontMap);
graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
graphics.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
graphics.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
graphics.setPaint(TRANSPARENT);
graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width, pgsize.height));
slides.get(i).draw(graphics);
g.drawImage(img, 0, i * (pgsize.height), null);

對於某些.ppt文件，背景顯示為黑色。 有誰知道這是什么原因以及如何解決這個問題？ 我懷疑用於創建.ppt文件的Office軟件可能是一個因素，但是我無法確認。

Answer 1

感謝您抽出寶貴的時間將示例上傳到我們的Bugzilla-請參閱＃61112

圖像的透明部分可以按照從圖像中剝離Alpha通道中所述進行替換，當然，您首先需要使用ARGB顏色模型。

我已經在示例中添加了Arial Unicode字體，但是您可能需要一個涵蓋所有使用的字符的不同字體 。

完整的例子：

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.GraphicsEnvironment;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.HashMap;
import java.util.Map;

import javax.imageio.ImageIO;

import org.apache.poi.sl.usermodel.SlideShow;
import org.apache.poi.sl.usermodel.SlideShowFactory;
import org.junit.Test;

public class TestRendering {

    @Test
    public void bug61112() throws Exception {
        Font font = Font.createFont(Font.TRUETYPE_FONT, new File("arialuni.ttf"));
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        ge.registerFont(font);

        SlideShow<?,?> ppt = SlideShowFactory.create(new File("bug61112.ppt"), null, true);
        double scale = 1;
        Dimension pgsize = ppt.getPageSize();
        int width = (int) (pgsize.width * scale);
        int height = (int) (pgsize.height * scale);

        BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        Graphics2D graphics = img.createGraphics();
        DrawFactory.getInstance(graphics).fixFonts(graphics);

        // default rendering options
        graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        graphics.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
        graphics.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);

        Map<String,String> fallbackMap = new HashMap<String,String>();
        fallbackMap.put("*", font.getFamily());
        graphics.setRenderingHint(Drawable.FONT_FALLBACK, fallbackMap);

        ppt.getSlides().get(0).draw(graphics);

        // Replace the transparent parts of the image
        // Set composite rules to paint "behind"
        graphics.setComposite(AlphaComposite.DstOver);
        graphics.setPaint(Color.WHITE);
        graphics.fillRect(0, 0, width, height);

        ImageIO.write(img, "PNG", new File("bla.png"));

        graphics.dispose();
        img.flush();


    }
}