如何将图像转换为PDF?

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【中文标题】如何将图像转换为PDF?【英文标题】:How to convert Image to PDF? 【发布时间】:2016-07-18 06:02:34 【问题描述】:

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

【问题讨论】:

Convert image to PDF in android的可能重复 您可以为此使用 itext 库。这是一个例子。 concretepage.com/itext/add-image-in-pdf-using-itext-in-java 我试过了。我在这里实现了该代码。我的问题是,PDF 中的图像非常小。 【参考方案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();

【讨论】:

我试过代码。部分工作,现在图像太大了。请找到更新的问题。我发布了几张图片 但是,它因图片而异。如果我从相机中选择图像,则对齐不正确。如果我选择不同质量的不同图像,对齐方式也会不同。如何动态解决此问题? 我不知道为什么它对另一个图像有任何影响。无论如何,您可以使用 setAlignment 方法修复它。再次更新,请检查答案。 @Suman,当您在 iText 中缩放 Image 对象时,您不会丢失任何信息:像素数保持不变。虽然 PDF 没有分辨率,但 PDF 中的图像有。当您缩小图像时(即:将相同数量的像素放在较小的画布上),分辨率会增加;放大时,分辨率会降低。所以质量是一样的,分辨率取决于图像大小和文档页面大小。 如您所知,它现在是实施 'com.itextpdf:itextpdf:5.5.13'【参考方案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!

【讨论】:

感谢代码,我试过了,它可以工作!但图像质量很差。我使用相机意图获取位图而不是选择文件。对于质量,可能是因为您在执行该操作时调整了位图的大小 bitmap = Bitmap.createScaledBitmap(bitmap, bitmap.getWidth(), bitmap.getHeight(), true); 最终,这段代码非常适合我。我有一张使用滚动视图创建的图像,因为它是平板电脑,所以它的分辨率超过 3000 * 10000。接受的答案只打印出图像的一部分,但这个解决方案打印出所有内容。 能否请您更新上面的源代码链接,它无法访问,或者可以建议任何适当的教程来创建适用于 android 的图像到 pdf 转换器应用程序【参考方案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()

【讨论】:

【参考方案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();


【讨论】:

在 android 12 上测试,工作正常 非常感谢,正是我想要的:)【参考方案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();
    

【讨论】:

如果你按照他们的许可使用这个库,你必须让你的应用开源!!!!【参考方案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();

    

【讨论】:

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