JavaScript基于pdf-lib实现图片转PDF工具

function readFileAsDataUrl(file) {
  return new Promise(function (resolve, reject) {
    var reader = new FileReader();
    reader.onload = function (event) {
      resolve(
        String(event.target && event.target.result ? event.target.result : ""),
      );
    };
    reader.onerror = function () {
      reject(new Error("file_read_failed"));
    };
    reader.readAsDataURL(file);
  });
}

function getPageSizePt(pageSize, orientation, imageWidth, imageHeight) {
  var widthPt;
  var heightPt;

  if (pageSize === "original") {
    widthPt = imageWidth * PX_TO_PT;
    heightPt = imageHeight * PX_TO_PT;
  } else {
    var pageSizeValue = PAGE_SIZES_MM[pageSize] || PAGE_SIZES_MM.a4;
    widthPt = pageSizeValue.width * MM_TO_PT;
    heightPt = pageSizeValue.height * MM_TO_PT;
  }

  // 省略方向交换逻辑
  return {
    widthPt: widthPt,
    heightPt: heightPt,
    orientation: finalOrientation,
  };
}

function drawImageToJpeg(image, rotation) {
  var angle = Number(rotation || 0);
  var swapSide = angle === 90 || angle === 270;
  var canvas = document.createElement("canvas");

  canvas.width = swapSide ? image.naturalHeight : image.naturalWidth;
  canvas.height = swapSide ? image.naturalWidth : image.naturalHeight;

  var context = canvas.getContext("2d", { alpha: false });
  context.fillStyle = "#ffffff";
  context.fillRect(0, 0, canvas.width, canvas.height);
  context.translate(canvas.width / 2, canvas.height / 2);
  context.rotate((angle * Math.PI) / 180);
  context.drawImage(image, -image.naturalWidth / 2, -image.naturalHeight / 2);

  return parseDataUrl(canvas.toDataURL("image/jpeg", 0.92));
}

async function buildPdfBlobWithPdfLib(pages, PDFDocument) {
  var pdfDocument = await PDFDocument.create();

  for (var i = 0; i < pages.length; i += 1) {
    var item = pages[i];
    var page = pdfDocument.addPage([item.pageWidthPt, item.pageHeightPt]);
    var jpg = await pdfDocument.embedJpg(item.imageBytes);
    page.drawImage(jpg, {
      x: item.xPt,
      y: item.yPt,
      width: item.drawWidthPt,
      height: item.drawHeightPt,
    });
  }

  var pdfBytes = await pdfDocument.save();
  return new Blob([pdfBytes], { type: "application/pdf" });
}