我需要将任意 PDF 文档的页面导出为 jpeg/png/etc 格式的一系列单个图像。我需要在 Java 中执行此操作。
尽管我确实了解 iText、PDFBox 和各种其他 java pdf 库,但我希望能找到一些工作示例或操作方法的指针。
谢谢。
这是一种方法,它结合了来自网络的一些代码片段。
如何将 PDF 绘制成图像?
https://pdf-renderer.dev.java.net/examples.html
从图像创建缓冲图像
原文:http ://www.exampledepot.com/egs/java.awt.image/Image2Buf.html
将生成的图形保存为 PNG 或 JPEG 文件
原文:http ://www.exampledepot.com/egs/javax.imageio/Graphic2File.html
更新:http : //docs.oracle.com/javase/tutorial/2d/images/saveimage.html
组合在一起就像这样将所有页面变成图像:
import com.sun.pdfview.PDFFile;
import com.sun.pdfview.PDFPage;
import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Transparency;
import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import javax.swing.*;
import javax.imageio.*;
import java.awt.image.*;
public class ImageMain {
public static void setup() throws IOException {
// load a pdf from a byte buffer
File file = new File("test.pdf");
RandomAccessFile raf = new RandomAccessFile(file, "r");
FileChannel channel = raf.getChannel();
ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
PDFFile pdffile = new PDFFile(buf);
int numPgs = pdffile.getNumPages();
for (int i = 0; i < numPgs; i++) {
// draw the first page to an image
PDFPage page = pdffile.getPage(i);
// get the width and height for the doc at the default zoom
Rectangle rect = new Rectangle(0, 0, (int) page.getBBox().getWidth(), (int) page.getBBox().getHeight());
// generate the image
Image img = page.getImage(rect.width, rect.height, // width & height
rect, // clip rect
null, // null for the ImageObserver
true, // fill background with white
true // block until drawing is done
);
// save it as a file
BufferedImage bImg = toBufferedImage(img);
File yourImageFile = new File("page_" + i + ".png");
ImageIO.write(bImg, "png", yourImageFile);
}
}
// This method returns a buffered image with the contents of an image
public static BufferedImage toBufferedImage(Image image) {
if (image instanceof BufferedImage) {
return (BufferedImage) image;
}
// This code ensures that all the pixels in the image are loaded
image = new ImageIcon(image).getImage();
// Determine if the image has transparent pixels; for this method's
// implementation, see e661 Determining If an Image Has Transparent
// Pixels
boolean hasAlpha = hasAlpha(image);
// Create a buffered image with a format that's compatible with the
// screen
BufferedImage bimage = null;
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
try {
// Determine the type of transparency of the new buffered image
int transparency = Transparency.OPAQUE;
if (hasAlpha) {
transparency = Transparency.BITMASK;
}
// Create the buffered image
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
bimage = gc.createCompatibleImage(image.getWidth(null), image.getHeight(null), transparency);
} catch (HeadlessException e) {
// The system does not have a screen
}
if (bimage == null) {
// Create a buffered image using the default color model
int type = BufferedImage.TYPE_INT_RGB;
if (hasAlpha) {
type = BufferedImage.TYPE_INT_ARGB;
}
bimage = new BufferedImage(image.getWidth(null), image.getHeight(null), type);
}
// Copy image to buffered image
Graphics g = bimage.createGraphics();
// Paint the image onto the buffered image
g.drawImage(image, 0, 0, null);
g.dispose();
return bimage;
}
public static boolean hasAlpha(Image image) {
// If buffered image, the color model is readily available
if (image instanceof BufferedImage) {
BufferedImage bimage = (BufferedImage) image;
return bimage.getColorModel().hasAlpha();
}
// Use a pixel grabber to retrieve the image's color model;
// grabbing a single pixel is usually sufficient
PixelGrabber pg = new PixelGrabber(image, 0, 0, 1, 1, false);
try {
pg.grabPixels();
} catch (InterruptedException e) {
}
// Get the image's color model
ColorModel cm = pg.getColorModel();
return cm.hasAlpha();
}
public static void main(final String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
try {
ImageMain.setup();
} catch (IOException ex) {
ex.printStackTrace();
}
}
});
}
}
如果您考虑 JPedal PDF 库,它是内置的,并在https://support.idrsolutions.com/hc/en-us/articles/115001978091-Convert-PDF-Files-to-Image上附有示例源文件
如果您发现 sun 渲染器不适用于您的所有 PDF 文档,您可以考虑使用 jPDFImages。
为了提高效率,您应该将每个 PDF 页面转换为缓冲图像,然后从那里转换为您需要的各种图像格式。这将避免必须从 PDF 转换为每种格式的图像。
这是使用 jPDFImages 从 PDF 转换为缓冲图像的链接:http: //kbdeveloper.qoppa.com/jpdfimages/codesampleconvertpdfpageintobufferedimageinjava
对于每个页面图像,您可以简单地导出为不同的图像格式: ImageIO.write(pageBufferedImage, "JPEG", outputFile); ImageIO.write(pageBufferedImage, "PNG", outputFile); ETC...
有不同的库可以做到这一点。我已经用PDFBox实现了这一点。但在我看来,最有效的解决方案是使用ghostscript。但是,如果您认为需要一个简单的解决方案,请使用ImageMagick。但是 ImageMagick 在内部调用了 ghostscript。使用 ghostscript 或 imagemagick 可以为您提供更好的解决方案。它比任何其他库都快得多。
PDF 到位图(Android 兼容代码)
File pdfFile = new File(filePath);
PdfRenderer renderer = new PdfRenderer(ParcelFileDescriptor.open(pdfFile, ParcelFileDescriptor.MODE_READ_ONLY));
final int pageCount = renderer.getPageCount();
//Currently for a page, iterate for all the pages
PdfRenderer.Page page = renderer.openPage(pageCount);
int width = page.getWidth();
int height = page.getHeight();
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
只需从 1 而不是 0 开始 for 循环。您的问题将得到解决。