我们可以使用颤振将PDF转换为图像以显示文件的缩略图吗？

Question

用例：为了在文件列表中显示 PDF 的缩略图。

问题 2：我们可以将 FPF 转换为图像以在列表中显示缩略图吗？

Answer 1

使用pdf_render 和image 插件。

import 'package:pdf_render/pdf_render.dart';
import 'package:image/image.dart' as imglib;


final doc = await PdfDocument.openFile('abc.pdf');
final pages = doc.pageCount;
List<imglib.Image> images = [];

// get images from all the pages
for (int i = 1; i <= pages; i++) {
  var page = await doc.getPage(i);
  var imgPDF = await page.render();
  var img = await imgPDF.createImageDetached();
  var imgBytes = await img.toByteData(format: ImageByteFormat.png);
  var libImage = imglib.decodeImage(imgBytes.buffer
      .asUint8List(imgBytes.offsetInBytes, imgBytes.lengthInBytes));
  images.add(libImage);
}

// stitch images
int totalHeight = 0;
images.forEach((e) {
  totalHeight += e.height;
});
int totalWidth = 0;
images.forEach((element) {
  totalWidth = totalWidth < element.width ? element.width : totalWidth;
});
final mergedImage = imglib.Image(totalWidth, totalHeight);
int mergedHeight = 0;
images.forEach((element) {
  imglib.copyInto(mergedImage, element, dstX: 0, dstY: mergedHeight, blend: false);
  mergedHeight += element.height;
});

// Save image as a file
final documentDirectory = await getExternalStorageDirectory();
File imgFile = new File('${documentDirectory.path}/abc.jpg');
new File(imgFile.path).writeAsBytes(imglib.encodeJpg(mergedImage));

Answer 2

正确答案：使用 Printing 和 pdf 插件，为了将 PDF 转换为图像，我们可以简单地通过以下方式实现：

// send pdfFile as params
imageFromPdfFile(File pdfFile) async {
    final document = await lib.PDFDocument.openFile(pdfFile.path);
    final page = await document.getPage(1);
    final pageImage = await page.render(width: page.width, height: page.height);
    await page.close();
    print(pageImage.bytes);

    //... now convert 
    // .... pageImage.bytes to image
}