Android PdfDocument.Page - 图像大小的问题 [英] Android PdfDocument.Page - Problems with image size

问题描述

在绘制到PdfDocument.Page时，我遇到了图像变大的问题。
该应用针对运行Android 4.4.4（API级别19）的设备。

I am experiencing problems with images being larger when drawing onto a PdfDocument.Page. The app is targeted for a device running Android 4.4.4 (API level 19).

我正在生成pdf文档并添加如下图像：

I am generating a pdf document and adding an image as follows:

PdfDocument document = new PdfDocument();

//Create an A4 sized page 595 x 842 in Postscript points.
PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(595, 842, 1).create();

PdfDocument.Page page = document.startPage(pageInfo);
Canvas canvas = page.getCanvas();

Bitmap logo = BitmapFactory.decodeResource(context.getResources(), R.drawable.pdf_logo);

Log.i(Consts.LOG_TAG, "pdf canvas density = " + canvas.getDensity());
Log.i(Consts.LOG_TAG, "pdf UOD logo density = " + logo.getDensity());

canvas.drawBitmap(logo, 50, 50, null);

document.finishPage(page);

/*
document is written out to a FileOuputStream().
Details omitted.
*/

文件我写得正确，我使用Canvas.drawText（）方法呈现的其他文本看起来很好。

但是，在pdf文档中绘制的图像总是太大。

我检查过图像和画布的密度是否相同。
图像（pdf_logo.jpg）是：

- 160 dpi

- 160 x 160分辨率的物理像素。

- 所以是1英寸x 1英寸大小。

上述代码中的日志也返回以下内容：

04-22 11:55： 50.607：I / App（7856）：pdf canvas density = 160

04-22 11：55：50.607：I / App（7856）：pdf UOD logo密度= 160

这表明图像dpi也与Canvas密度相匹配。
但是，当图像被绘制到pdf文档上时，图像远大于1英寸x 1英寸。它的尺寸大约是2英寸x 2英寸的两倍。

我怀疑Android使用了图像的物理分辨率（160 x 160）并将其转换为PdfDocument.Page大小单位，Postscript点为1/72英寸。所以160个Postscript点相当于2.2英寸〜原始图像尺寸的两倍（1 x 1英寸）。

如果我将图像的大小减半，那么我会得到像素化，因为它实际上会将0.5 x 0.5英寸的图像绘制成1 x 1英寸的空间。

我想知道如何在PdfDocument.Page上绘制图像作为实际尺寸，而不会出现这些缩放/尺寸问题。

The document is written out correctly, and other text I have rendered using Canvas.drawText() method looks fine.
However, the image drawn is always too big in the pdf document.

I have checked the density of both the image and canvas are the same. The image (pdf_logo.jpg) is:
- 160 dpi
- 160 x 160 physical pixels in resolution.
- So is 1 inch x 1 inch in size.

The logs in the above code also returned the following:

04-22 11:55:50.607: I/App(7856): pdf canvas density = 160
04-22 11:55:50.607: I/App(7856): pdf UOD logo density = 160

This shows that the image dpi matches the Canvas density as well. However, when the image is drawn onto the pdf document, the image is much larger than 1 inch x 1 inch. It is about double the size , just over 2 inch x 2 inch.

My suspicion is that Android has used the physical resolution of the image (160 x 160) and converted it into the PdfDocument.Page size units, Postscript points which are 1/72 inch. So 160 Postscript points equates to 2.2 inches ~ double the size of the original image (1 x 1 inch).

If I halve the size of the image then I get pixelation, as it will effectively be drawing an 0.5 x 0.5 inch image into a 1 x 1 inch space.

I would like to know how I can draw an image as actual size on a PdfDocument.Page, without having these scaling/size issues.

推荐答案

根据要求，我发现的解决方案是将密度设置为高于应有的值。
将位图密度设置为 DENSITY_XHIGH 而不是 DENSITY_HIGH 为我提供了相当大的渲染位图。位图更接近于生成pdf时我期望的大小。

As requested, the solution I found was to set the density to a value higher than what it should be. Setting the bitmap density to DENSITY_XHIGH instead of DENSITY_HIGH improved the rendered bitmap considerably for me. The bitmap is closer to the size I would expect when the pdf is generated.

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