What is the DPI resolution value of PDF document? - ByteScout
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What is the DPI resolution value of PDF document?

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PDF is a vector-based format entity and there are no “classic” dots (pixels) as one may find in JPG, PNG, TIFF pictures. In opposite, PDF format internally uses something similar to computer programs that can draw lines, circles, text, forms, etc. So PDF file is automatically executed to create a picture for various DPI (Dots Per Inch) targeting screen or printing device depending on specific monitors or printing devices accordingly.

All too often, DPI and PPI are used interchangeably even though the means are different. Specifically, DPI (Dots Per Inch), is that measurement more refers to the resolution of a computer printer. While PPI (Pixels Per Inch) or pixel density is synonymous with samples per inch.

It refers to the measurement of the resolution of a computer display, correlated to the size of the display in inches and the total number of pixels in the horizontal and vertical directions. For instance, a 300 dpi PDF is a document that contains raster information sized to 300 PPI at the defined output dimensions.

Why is it important to know the DPI resolution of a document?

PDF files do not have a single DPI value, all bitmap page objects have separate resolutions, therefore, course vector objects such as text have no resolution at all. However, this flexibility allows PDF documents to be printed and displayed with the highest quality even for super large sizes. If you compare this to JPG, PNG pictures then pictures are just a set of pixels and you will see blurring effects when pictures are zoomed in or increased in size.

PDF files were designed to look crisp and clean but not bit-mapped or pixellated. Despite this, the better quality PDF files are usually larger. Many designs and photo apps suggest that files should be saved as PDFs. Though having clunky PDFs are great for printing but it might useful for other purposes. For instance, you might need to transfer files or upload them into a cloud network. One way to solve this is to convert PDFs into another format while maintaining a high DPI.

How to convert documents to have a better DPI for high-quality?

So if you need to convert PDF into a JPG, PNG or TIFF picture then you should use PDF Renderer SDK and just set size and resolution of output picture with a given resolution. And the SDK will render PDF documents into a picture with the desired picture resolution (300 to 600 DPI for high-quality pictures). So you should not worry about the resolution of the source PDF but just need to define output picture size with the same aspect ratio as the source PDF. It allows printing from within the application.

Each of the file formats has its own benefits. JPG files offer adjustable compression with high resolution and smaller file size. PNG files may be slightly bigger than JPG but these files have greater compressibility and also supports transparency. TIFF files allow lossless compression which makes it possible to edit and resave without losing image quality. It can also convert PDF to BMP, PDF to EMF, and PDF to multi-page TIFF.

For simplicity, when you are creating PDF document using tools like PDF SDK (PDF Generator SDK) then these tools are using coordinates calculated using 72 dots per inch (but this can be changed using .Resolution property in the SDK). But, again, this “default” DPI value in PDF Generator SDK tool is just for having a way to comfortably use coordinates to add lines, text, form elements, images (and other object types) and you may create thumbnail or print PDF using any other required resolution and output size.

PDF Renderer SDK is great to use since it renders different fonts with any styling, renders vector graphics as well as images. It works offline and doesn’t require a constant Internet connection. It also does not require any other PDF reader software such as Adobe Reader to be installed. It supports .NET, ASP.NET and Visual Basic 6 applications with both x86 and x64 mode.

How to change the DPI on a document?

As discussed, the DPI can affect the quality of the output when printing. The settings that will change the appearance of PDF or image output will involve either compressing the file or changing the DPI. Compressing the files can be done right within a PDF reader.

The DPI setting of a printer will relay information to the printing program which has a dialogue box where you can change the DPI settings as well as other parameters. When you go to printing preferences in the printing program, find the advanced settings. Once that is opened you can change the DPI under Graphic-Print Quality before printing the document. On average a DPI of 300 is decent and offers a good quality output and a reasonable file size.


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