在Android中生成Pdf的缩略图

Question

我想从 pdf 文件生成图像（缩略图），就像 WhatsApp 所做的那样，如下所示

我已经尝试过了

1. PDFBox（https://github.com/TomRoush/PdfBox-Android）
2. Tika（编译 'org.apache.tika:tika-parsers:1.11'）
3. AndroidPdfViewer（https://github.com/barteksc/AndroidPdfViewer）

并且仍然无法找到从 pdf 生成图像的方法。

---

PDFBox：

有一个 github 问题可以解决这个问题（https://github.com/TomRoush/PdfBox-Android/issues/3），但这仍然没有解决。

注意：我成功地使用PDFBOX

从PDF中提取图像

---

AndroidPdfViewer：

Github 问题 (https://github.com/barteksc/AndroidPdfViewer/issues/49)

Answer 1

使用 PdfiumAndroid，如 barteksc 此处所述。

2021年还在工作...

生成 Pdf 缩略图的示例代码

//PdfiumAndroid (https://github.com/barteksc/PdfiumAndroid)
//https://github.com/barteksc/AndroidPdfViewer/issues/49
void generateImageFromPdf(Uri pdfUri) {
    int pageNumber = 0;
    PdfiumCore pdfiumCore = new PdfiumCore(this);
    try {
        //http://www.programcreek.com/java-api-examples/index.php?api=android.os.ParcelFileDescriptor
        ParcelFileDescriptor fd = getContentResolver().openFileDescriptor(pdfUri, "r");
        PdfDocument pdfDocument = pdfiumCore.newDocument(fd);
        pdfiumCore.openPage(pdfDocument, pageNumber);
        int width = pdfiumCore.getPageWidthPoint(pdfDocument, pageNumber);
        int height = pdfiumCore.getPageHeightPoint(pdfDocument, pageNumber);
        Bitmap bmp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        pdfiumCore.renderPageBitmap(pdfDocument, bmp, pageNumber, 0, 0, width, height);
        saveImage(bmp);
        pdfiumCore.closeDocument(pdfDocument); // important!
    } catch(Exception e) {
        //todo with exception
    }
}

public final static String FOLDER = Environment.getExternalStorageDirectory() + "/PDF";
private void saveImage(Bitmap bmp) {
    FileOutputStream out = null;
    try {
        File folder = new File(FOLDER);
        if(!folder.exists())
            folder.mkdirs();
        File file = new File(folder, "PDF.png");
        out = new FileOutputStream(file);
        bmp.compress(Bitmap.CompressFormat.PNG, 100, out); // bmp is your Bitmap instance
    } catch (Exception e) {
        //todo with exception
    } finally {
        try {
            if (out != null)
                out.close();
        } catch (Exception e) {
            //todo with exception
        }
    }
}

---

更新：

将库包含在 build.gradle 中

implementation 'com.github.barteksc:android-pdf-viewer:3.2.0-beta.1'

用于生成任何 PDF 页面的图像：

通过传递存储在存储中的任何 PDF uri 来调用方法 generateImageFromPdf(uri)。

该方法将在您存储的 PDF 文件夹中生成 PDF.png。

Answer 2

使用Android PDFRenderer组件

with(context) {
    contentResolver.openFileDescriptor(uri, "r")?.use { parcelFileDescriptor ->
        val pdfRenderer = PdfRenderer(parcelFileDescriptor).openPage(0)
        val bitmap = Bitmap.createBitmap(pdfRenderer.width, pdfRenderer.height, Bitmap.Config.ARGB_8888)
        pdfRenderer.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY)
        pdfRenderer.close()      
    }
}

Answer 3

val file = Constant.allMediaList[position]
val filename = Environment.getExternalStoragePublicDirectory(file)
if (file != null) {
    if (file.endsWith(".pdf")){
        val fd :ParcelFileDescriptor= ParcelFileDescriptor.open(filename,ParcelFileDescriptor.MODE_READ_WRITE)
        val pageNum: Int  = 0;
        val pdfiumCore: PdfiumCore  = PdfiumCore(mContext);
        try {
            val pdfDocument: PdfDocument = pdfiumCore.newDocument(fd);
            pdfiumCore.openPage(pdfDocument, pageNum);
            val width:  Int  = pdfiumCore.getPageWidthPoint(pdfDocument, pageNum);
            val height:  Int = pdfiumCore.getPageHeightPoint(pdfDocument, pageNum);

            // ARGB_8888 - best quality, high memory usage, higher possibility of OutOfMemoryError
            // RGB_565 - little worse quality, twice less memory usage
            val bitmap: Bitmap = Bitmap.createBitmap(width, height,
                  Bitmap.Config.RGB_565);
            pdfiumCore.renderPageBitmap(pdfDocument, bitmap, pageNum, 0, 0,width, height);
            //if you need to render annotations and form fields, you can use
            //the same method above adding 'true' as last param

            Glide.with(mContext)
                .load(bitmap).into(holder.thumbnail)

            pdfiumCore.closeDocument(pdfDocument); // important!
        } catch(ex: IOException) {
            ex.printStackTrace();
            Toast.makeText(mContext,"failed",Toast.LENGTH_LONG).show()
        }

    }

Answer 4

Bitmap myBitmap = generateImageFromPdf(FileProvider.getUriForFile(context, context.getApplicationContext().getPackageName() + ".provider", Pdf_File.get(position).getAbsoluteFile()));
    holder.iv_icon.setImageBitmap(myBitmap);

}

Bitmap generateImageFromPdf(Uri pdfUri) {
    int pageNumber = 0;
    PdfiumCore pdfiumCore = new PdfiumCore(context);
    Bitmap bmp = null;
    try {
        //http://www.programcreek.com/java-api-examples/index.php?api=android.os.ParcelFileDescriptor
        ParcelFileDescriptor fd = context.getContentResolver().openFileDescriptor(pdfUri, "r");
        PdfDocument pdfDocument = pdfiumCore.newDocument(fd);
        pdfiumCore.openPage(pdfDocument, pageNumber);
        int width = pdfiumCore.getPageWidthPoint(pdfDocument, pageNumber);
        int height = pdfiumCore.getPageHeightPoint(pdfDocument, pageNumber);
        Log.e("Width_height", "" + width + " " + height);
        bmp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        pdfiumCore.renderPageBitmap(pdfDocument, bmp, pageNumber, 0, 0, width, height);
        pdfiumCore.closeDocument(pdfDocument);
    } catch (Exception e) {
        //todo with exception
    }
    return bmp;
}

Answer 5

这对我有用。在爪哇。

ParcelFileDescriptor parcelFileDescriptor = contentResolver.openFileDescriptor(uriFile, "r");
try (PdfRenderer pdfRenderer = new PdfRenderer(parcelFileDescriptor);
     PdfRenderer.Page page = pdfRenderer.openPage(0)) {

    Bitmap bitmap = Bitmap.createBitmap(THUMBNAIL_WIDTH, THUMBNAIL_HEIGHT, Bitmap.Config.ARGB_8888);
    page.render(bitmap, null, null, PdfRenderer.Page.RENDER_MODE_FOR_DISPLAY);

    try (FileOutputStream fos = new FileOutputStream(thumbnailPath.toFile())) {
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
        fos.flush();

    }

} catch (Exception e) {
    Log.e(TAG, "Error creating thumbnail", e);

}