如何将图像转换为PDF？

Question

我正在开发一个需要将图像转换为 PDF 的应用程序。我尝试了一些方法，但问题是，该 PDF 中的图像尺寸非常小。我需要解决方案来解决这个问题。我也在寻找将多个图像转换为单个 PDF 文档。 我将发布我尝试过的代码。

    public void convertPDF(byte[] path)
{
 String FILE = "mnt/sdcard/FirstPdf.pdf";
    Document document=new Document();
    try {
        PdfWriter.getInstance(document, new FileOutputStream(FILE));
        document.open();

        try {
            image=Image.getInstance(path);
            document.add(new Paragraph("My Heading"));
            document.add(image);
            document.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    } catch (DocumentException e) {
        e.printStackTrace();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}

当我将位图转换为字节数组时，我正在压缩图像，我猜这就是原因。如果不压缩图像，我无法将位图转换为字节数组。

 ByteArrayOutputStream stream = new ByteArrayOutputStream();
        bmp.compress(Bitmap.CompressFormat.PNG,100,stream);
        byte[] byteArray=stream.toByteArray();
        convertPDF(byteArray);

有什么解决办法吗？

更新

在这里，我已经实现了@Burak Cakir 在答案中建议的答案。但现在我在 PDF 中获得了更大的图像。为了更好地理解，请找到下面的图片。

实际的图像是

Answer 1

我建议你使用iText pdf 库。这是gradle 依赖：

implementation 'com.itextpdf:itextg:5.5.10'

 Document document = new Document();

 String directoryPath = android.os.Environment.getExternalStorageDirectory().toString();

 PdfWriter.getInstance(document, new FileOutputStream(directoryPath + "/example.pdf")); //  Change pdf's name.

 document.open();

 Image image = Image.getInstance(directoryPath + "/" + "example.jpg");  // Change image's name and extension.

 float scaler = ((document.getPageSize().getWidth() - document.leftMargin()
               - document.rightMargin() - 0) / image.getWidth()) * 100; // 0 means you have no indentation. If you have any, change it.
 image.scalePercent(scaler);
 image.setAlignment(Image.ALIGN_CENTER | Image.ALIGN_TOP); 

 document.add(image);
 document.close();

Answer 2

从这里下载源代码 (Convert Image to pdf in android programmatically)

MainActivity.java：

package com.deepshikha.convertbitmap;

import android.Manifest;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.pdf.PdfDocument;
import android.net.Uri;
import android.provider.MediaStore;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Display;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    public static final int GALLERY_PICTURE = 1;
    Button btn_select, btn_convert;
    ImageView iv_image;
    boolean boolean_permission;
    boolean boolean_save;
    Bitmap bitmap;
    public static final int REQUEST_PERMISSIONS = 1;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
        listener();
        fn_permission();
    }

    private void init() {
        btn_select = (Button) findViewById(R.id.btn_select);
        btn_convert = (Button) findViewById(R.id.btn_convert);
        iv_image = (ImageView) findViewById(R.id.iv_image);
    }

    private void listener() {
        btn_select.setOnClickListener(this);
        btn_convert.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn_select:
                Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                startActivityForResult(intent, GALLERY_PICTURE);
                break;

            case R.id.btn_convert:
                if (boolean_save){

                    Intent intent1=new Intent(getApplicationContext(),PDFViewActivity.class);
                    startActivity(intent1);

                }else {
                    createPdf();
                }
                break;


        }
    }

    private void createPdf(){
        WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
        Display display = wm.getDefaultDisplay();
        DisplayMetrics displaymetrics = new DisplayMetrics();
        this.getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
        float hight = displaymetrics.heightPixels ;
        float width = displaymetrics.widthPixels ;

        int convertHighet = (int) hight, convertWidth = (int) width;

//        Resources mResources = getResources();
//        Bitmap bitmap = BitmapFactory.decodeResource(mResources, R.drawable.screenshot);

        PdfDocument document = new PdfDocument();
        PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(bitmap.getWidth(), bitmap.getHeight(), 1).create();
        PdfDocument.Page page = document.startPage(pageInfo);

        Canvas canvas = page.getCanvas();


        Paint paint = new Paint();
        paint.setColor(Color.parseColor("#ffffff"));
        canvas.drawPaint(paint);



        bitmap = Bitmap.createScaledBitmap(bitmap, bitmap.getWidth(), bitmap.getHeight(), true);

        paint.setColor(Color.BLUE);
        canvas.drawBitmap(bitmap, 0, 0 , null);
        document.finishPage(page);


        // write the document content
        String targetPdf = "/sdcard/test.pdf";
        File filePath = new File(targetPdf);
        try {
            document.writeTo(new FileOutputStream(filePath));
            btn_convert.setText("Check PDF");
            boolean_save=true;
        } catch (IOException e) {
            e.printStackTrace();
            Toast.makeText(this, "Something wrong: " + e.toString(), Toast.LENGTH_LONG).show();
        }

        // close the document
        document.close();
    }



    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == GALLERY_PICTURE && resultCode == RESULT_OK) {

            if (resultCode == RESULT_OK) {
                Uri selectedImage = data.getData();
                String[] filePathColumn = {MediaStore.Images.Media.DATA};

                Cursor cursor = getContentResolver().query(
                        selectedImage, filePathColumn, null, null, null);
                cursor.moveToFirst();

                int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                String filePath = cursor.getString(columnIndex);
                cursor.close();


                bitmap = BitmapFactory.decodeFile(filePath);
                iv_image.setImageBitmap(bitmap);


                btn_convert.setClickable(true);
            }
        }
    }

    private void fn_permission() {
        if ((ContextCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED)||
                (ContextCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED)) {

            if ((ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, android.Manifest.permission.READ_EXTERNAL_STORAGE))) {
            } else {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{android.Manifest.permission.READ_EXTERNAL_STORAGE},
                        REQUEST_PERMISSIONS);

            }

            if ((ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE))) {
            } else {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                        REQUEST_PERMISSIONS);

            }
        } else {
            boolean_permission = true;


        }
    }
    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_PERMISSIONS) {

            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                boolean_permission = true;


            } else {
                Toast.makeText(getApplicationContext(), "Please allow the permission", Toast.LENGTH_LONG).show();

            }
        }
    }


}

谢谢！

Answer 3

您可以将 JPG 转换为 PDF，方法是使用至少 19 个 SDK (KitKat 4.4) 并使用 Google 的 PdfDocument API (https://developer.android.com/reference/android/graphics/pdf/PdfDocument)，如下面的 Kotlin 所示：

    // Load JPG file into bitmap
    val f: File = myJPGFile
    val bitmap: Bitmap  = BitmapFactory.decodeFile(f.absolutePath)

    // Create a PdfDocument with a page of the same size as the image
    val document: PdfDocument = PdfDocument()
    val pageInfo: PdfDocument.PageInfo  = PdfDocument.PageInfo.Builder(bitmap.width, bitmap.height, 1).create()
    val page: PdfDocument.Page  = document.startPage(pageInfo)

    // Draw the bitmap onto the page
    val canvas: Canvas = page.canvas
    canvas.drawBitmap(bitmap, 0f, 0f, null)
    document.finishPage(page)

    // Write the PDF file to a file
    val directoryPath: String  = android.os.Environment.getExternalStorageDirectory().toString()
    document.writeTo( FileOutputStream(directoryPath + "/example.pdf"))
    document.close()

Answer 4

只需传递上下文和文件列表 它将在缓存目录中创建一个 PDF 文件 添加您自己的逻辑以共享/打开 PDF 工作快速可靠的方法

• 无需库（使用 android 内部 android.graphics.pdf.PdfDocument 类）
• 在后台工作，不会冻结 UI
• 无需声明和授予存储权限:)

private static void createPdf(Context context,ArrayList<File> data){
    File pdfFile = new File(context.getExternalCacheDir().getAbsolutePath() + File.separator + "TemperoryPDF_"+System.currentTimeMillis()+".pdf");
    Toast.makeText(context, "Creating PDF,Please wait..", Toast.LENGTH_SHORT).show();
    new AsyncTask<Void, Void, Void>() {
        @Override
        protected Void doInBackground(Void... voids) {
            PdfDocument document = new PdfDocument();
            try {
                for(File item:data) {
                    Bitmap bitmap = BitmapFactory.decodeFile(item.getAbsolutePath());
                    PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(bitmap.getWidth(), bitmap.getHeight(), 1).create();
                    PdfDocument.Page page = document.startPage(pageInfo);
                    Canvas canvas = page.getCanvas();
                    Paint paint = new Paint();
                    paint.setColor(Color.parseColor("#ffffff"));
                    canvas.drawPaint(paint);
                    canvas.drawBitmap(bitmap, 0, 0, null);
                    document.finishPage(page);
                }
                document.writeTo(new FileOutputStream(pdfFile));
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                document.close();
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void unused) {
            super.onPostExecute(unused);
            if(pdfFile.exists() && pdfFile.length()>0) {
                FileUtil.openFile(context, pdfFile.getAbsolutePath()); // See: https://gist.github.com/omkar-tenkale/34d3aa1966653e6949d1ddaee1ba3355
            }else {
                Toast.makeText(context, "Something went wrong creating the PDF :(", Toast.LENGTH_SHORT).show();
            }
        }
    }.execute();

}

Answer 5

在 gradle 中添加库

implementation 'com.itextpdf:itextg:5.5.10'

创建文件夹路径 - 它将从文件夹的所有图像创建 pdf

File folderPath = new File(Environment.getExternalStorageDirectory() + "/YourImagesFolder");

File[] imageList = folderPath .listFiles();
ArrayList<File> imagesArrayList = new ArrayList<>();
for (File absolutePath : imageList) {
          imagesArrayList.add(absolutePath);
}
new CreatePdfTask(context, imagesArrayList).execute();

异步任务

 public class CreatePdfTask extends AsyncTask<String, Integer, File> {
    Context context;
    ArrayList<File> files;
    ProgressDialog progressDialog;

    public CreatePdfTask(Context context2, ArrayList<File> arrayList) {
        context = context2;
        files = arrayList;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = new ProgressDialog(context);
        progressDialog.setTitle("Please wait...");
        progressDialog.setMessage("Creating pdf...");
        progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        progressDialog.setIndeterminate(false);
        progressDialog.setMax(100);
        progressDialog.setCancelable(true);
        progressDialog.show();
    }

    @Override
    protected File doInBackground(String... strings) {
        File outputMediaFile = Constant.getPdfPath();//path in which you want to save pdf

        Document document = new Document(PageSize.A4, 38.0f, 38.0f, 50.0f, 38.0f);
        try {
            PdfWriter.getInstance(document, new FileOutputStream(outputMediaFile));
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return null;
        }
        document.open();

        int i = 0;
        while (true) {
            if (i < this.files.size()) {
                try {
                    Image image = Image.getInstance(files.get(i).getAbsolutePath());

                    float scaler = ((document.getPageSize().getWidth() - document.leftMargin()
                            - document.rightMargin() - 0) / image.getWidth()) * 100; // 0 means you have no indentation. If you have any, change it.
                    image.scalePercent(scaler);
                    image.setAlignment(Image.ALIGN_CENTER | Image.ALIGN_TOP);
                    image.setAbsolutePosition((document.getPageSize().getWidth() - image.getScaledWidth()) / 2.0f,
                            (document.getPageSize().getHeight() - image.getScaledHeight()) / 2.0f);

                    document.add(image);
                    document.newPage();
                    publishProgress(i);
                    i++;
                } catch (BadElementException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (DocumentException e) {
                    e.printStackTrace();
                }
            } else {
                document.close();
                return outputMediaFile;
            }
        }
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
        this.progressDialog.setProgress(((values[0] + 1) * 100) / this.files.size());
        StringBuilder sb = new StringBuilder();
        sb.append("Processing images (");
        sb.append(values[0] + 1);
        sb.append("/");
        sb.append(this.files.size());
        sb.append(")");
        progressDialog.setTitle(sb.toString());
    }

    @Override
    protected void onPostExecute(File file) {
        super.onPostExecute(file);
        progressDialog.dismiss();
        Toast.makeText(context, "Pdf store at " + file.getAbsolutePath(), Toast.LENGTH_SHORT).show();
    }
}

Answer 6

这就是我将图片转换成pdf的方法，你需要先在manifest中声明用户权限

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

然后在您的主要活动中，您必须检查是否已授予权限，如果您不知道该怎么做，只需在 youtube 上搜索，您会发现很多关于该主题的视频，然后，我使用此方法将我想从图库中转换为 pdf 的图片。

public void pickImage() {
    Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    startActivityForResult(intent,120);
}

之后我重写 onActivityResult() 方法来检索所选图像。

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 120 && resultCode == RESULT_OK && data != null) {
        Uri selectedImageUri = data.getData();

        String[] filePath = {MediaStore.Images.Media.DATA};
        Cursor cursor =getContentResolver().query(selectedImageUri,filePath,null,null,null);
        cursor.moveToFirst();

        int columnIndex = cursor.getColumnIndex(filePath[0]);
        String myPath = cursor.getString(columnIndex);
        cursor.close();

        Bitmap bitmap = BitmapFactory.decodeFile(myPath);
        imageView.setImageBitmap(bitmap);

        PdfDocument pdfDocument = new PdfDocument();
        PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(bitmap.getWidth(),
                bitmap.getHeight(),1).create();
        PdfDocument.Page page = pdfDocument.startPage(pageInfo);

        Canvas canvas = page.getCanvas();
        Paint paint = new Paint();
        paint.setColor(Color.parseColor("#FFFFFF"));
        canvas.drawPaint(paint);

        bitmap=Bitmap.createScaledBitmap(bitmap,bitmap.getWidth(),bitmap.getHeight(),true);
        paint.setColor(Color.BLUE);
        canvas.drawBitmap(bitmap,0,0,null);

        pdfDocument.finishPage(page);

        //save the bitmap image
        File root = new File(Environment.getExternalStorageDirectory(),"PDF folder 12");
        if (!root.exists()){
            root.mkdir();
        }
        File file = new File(root,"picture.pdf");
        try {
            FileOutputStream fileOutputStream = new FileOutputStream(file);
            pdfDocument.writeTo(fileOutputStream);
        }catch (Exception e){
            e.getStackTrace();
        }
        pdfDocument.close();
    }
}

不要忘记权限，请用户授予权限

如果要自动打开pdf文件，请在给出正确的文件夹路径和pdf文件名后使用此方法

 String path ="/sdcard/PDF folder 12/picture.pdf";
public void openPDF (){
    File pdfFile = new File(path);//File path
    if (pdfFile.exists()) //Checking if the file exists or not
    {
        Uri path = Uri.fromFile(pdfFile);
        Intent objIntent = new Intent(Intent.ACTION_VIEW);
        objIntent.setDataAndType(path, "application/pdf");
        objIntent.setFlags(Intent. FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(objIntent);//Starting the pdf viewer
    } else {

        Toast.makeText(GenerateQRActivity.this, "The file not exists! ", Toast.LENGTH_SHORT).show();

    }
}