Technical Specifications 2 of 7
Dimensions
PNG records image width and height in pixels in the IHDR chunk. Both values are four-byte unsigned integers, are limited by the PNG integer rules to 2,147,483,647, and cannot be zero.
The specification limit is not a practical production limit. Applications, memory, file storage, upload limits, RIP software, and production equipment generally impose much smaller maximum dimensions.
Dimension concepts
| Property | Meaning |
|---|---|
| Pixel width | Number of pixel columns in the image |
| Pixel height | Number of pixel rows in the image |
| Aspect ratio | Relationship between width and height |
| Physical output size | How the available pixels are distributed across the produced width and height |
| Pixel aspect ratio | Optional intended pixel shape information that may be stored in pHYs |
For production, validate the actual pixel dimensions against the intended physical size and the maker's required effective resolution.