PNG is a lossless image format, but that does not mean every PDF-to-PNG conversion has the same quality. The main quality decision is usually the rasterization resolution: how many pixels are created from each PDF page.
What determines PNG quality?
Resolution, page dimensions, source content and the conversion engine all matter. A PDF containing small text needs enough pixels to represent character edges clearly. A simple diagram may need less resolution than a detailed page.
Understanding DPI
DPI is commonly used to describe rasterization resolution. Higher values generally create larger images with more detail. The best setting is not automatically the highest available one; excessive resolution increases storage and processing costs without helping the intended use.
Practical starting points
For screen viewing, a moderate resolution is often sufficient. For documents that will be printed or inspected closely, a higher resolution may be appropriate. Test a representative page containing the smallest text you need to preserve.
PNG versus JPG for PDF pages
PNG preserves sharp edges without lossy compression and is often a good fit for text-heavy pages. JPG can be much smaller for photographs, but compression artifacts can become visible around small text and fine lines.
How to check the result
- Open a converted page at 100% scale.
- Inspect the smallest important text.
- Check thin lines and tables.
- Compare file size with the intended use.
- Increase resolution only if the current result is not readable.
Use the PDF-to-image tool
Use the Tervilo PDF to Images tool when you need PNG page images, then check the resulting pixel dimensions and readability.
Pixel dimensions matter more than a number alone
DPI is useful when you know the intended physical page size, but the actual output pixel dimensions are what the screen or image editor receives. Check both when comparing conversions.
Test the hardest page
Choose a page with small text, tables or fine lines as your test page. If that page remains readable, the rest of a simpler document is more likely to convert successfully at the same setting.
Practical example
Suppose a scanned form contains small 9-point text. Convert one representative page at a moderate resolution and inspect the smallest text at 100% scale. If characters look soft or thin lines disappear, increase the resolution and compare file size. Once the smallest important content is clear, there is usually little benefit in going dramatically higher.