缩放图像模糊PDFBox [英] Scaled image blurry in PDFBox

问题描述

我正在尝试将尺寸= 2496 x 3512的图像缩放为PDF文档。我正在使用PDFBox生成它，但缩放的图像最终模糊。

I'm trying to scaling an image with size = 2496 x 3512 into a PDF document. I'm using PDFBox to generate it but the scaled image ends up blurred.

以下是一些片段：

• PDF页面大小（A4）由page.findMediaBox（）返回.createDimension（）：java.awt.Dimension [width = 612，height = 792]

• PDF Page size (A4) returned by page.findMediaBox().createDimension(): java.awt.Dimension[width=612,height=792]

然后我根据页面大小与图像大小计算缩放维度，返回：java.awt.Dimension [width = 562，height = 792]
我使用下面的代码是为了计算缩放尺寸：

Then I calculate the scaled dimension based on the Page size vs. Image size which returns: java.awt.Dimension[width=562,height=792] I use the code below in order to calculate the scaled dimension:

public static Dimension getScaledDimension(Dimension imgSize, Dimension boundary) {
  int original_width = imgSize.width;
  int original_height = imgSize.height;
  int bound_width = boundary.width;
  int bound_height = boundary.height;
  int new_width = original_width;
  int new_height = original_height;

  // first check if we need to scale width
  if (original_width > bound_width) {
    //scale width to fit
    new_width = bound_width;
    //scale height to maintain aspect ratio
    new_height = (new_width * original_height) / original_width;
  }

  // then check if we need to scale even with the new height
  if (new_height > bound_height) {
    //scale height to fit instead
    new_height = bound_height;
    //scale width to maintain aspect ratio
    new_width = (new_height * original_width) / original_height;
  }

  return new Dimension(new_width, new_height);
}

实际执行图像缩放我正在使用Image Scalr API：

And to actually perform the image scaling I'm using Image Scalr API:

BufferedImage newImg = Scalr.resize(img, Scalr.Method.ULTRA_QUALITY, Scalr.Mode.FIT_EXACT, 
  scaledWidth, scaledHeight, Scalr.OP_ANTIALIAS);

我的问题是我做错了什么？缩放到较小尺寸时，不应模糊大图像。这是与PDF页面分辨率/大小相关的内容吗？

My question is what am I doing wrong? A big image shouldn't be blurred when scaled to a smaller size. Is this something related to the PDF page resolution/size?

谢谢，

Gyo

推荐答案

好的，我找到了一种在不损失质量的情况下添加图片的方法。

Ok, I found a way to add images without losing the quality.

实际上，为了使图像不被模糊，我让PDFBox通过给出所需的大小来调整图像的大小。与下面的代码类似：

Actually to make the image not be blurred I let PDFBox to resize the image by giving it the desired size. Like the code below:

PDXObjectImage ximage = new PDJpeg(doc, new FileInputStream(new File("/usr/gyo/my_large_image.jpg")), 1.0f);
PDPageContentStream contentStream = new PDPageContentStream(doc, page, true, false);
Dimension scaledDim = getScaledDimension(new Dimension(ximage.getWidth(),  ximage.getHeight()), page.getMediaBox().createDimension());
contentStream.drawXObject(ximage, 1, 1, scaledDim.width, scaledDim.height);
contentStream.close();

谢谢，

Gyo

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