understanding image file formats
Understanding different file formats can help you make informed purchasing decisions when you’re shopping for digital coloring pages.
There are loads of different file formats, so I’m going to keep this as simple as possible and limit the list to the ones most used for coloring pages.
WHY DOES IT MATTER WHICH FILE FORMAT IS USED?
Which image file format you save an image as can determine things like the color profile, how sharp it looks, or how much storage space it takes up on your computer. Not all formats can be – or are optimal for – printing.
WHAT IS IMAGE COMPRESSION?
Image compression is a way to reduce the size of an image file. In this context, size has nothing to do with the dimensions of the image – what we’re talking about is how much storage space it takes up on your computer.
For example: When I create new coloring pages, I often sketch them on paper first, but I always finalize them in Photoshop, working with the image as a PSD-file.
The image dimensions are equal to that of an A4-sized paper (210x297 mm), but because of the complexities of the PSD-file, it usually ends up being somewhere between 50-300 MB (megabytes). PSD is also a file type most people can’t open because it requires a Photoshop license.
To make the coloring pages available to others, and to reduce the file-size, I have to save them as a different file format; I use a combination of PDF and PNG.
The image dimensions are the same (210x297 mm), but the file size is drastically reduced – my PDF and PNG coloring pages usually end up being somewhere between 1-3 MB.
The more you can compress an image without losing quality, the better.
IMAGE QUALITY: LOSSLESS OR LOSSY COMPRESSION?
There are two main categories of image compression.
Lossless compression
It means that no information is lost – in other words, the quality of the image is preserved, even though the file size is reduced.
Lossy compression
It means that some information is in fact lost, resulting in an even smaller file size. But it also means that the quality of the image is somewhat reduced. However; often the quality reduction is so small that the human eye can’t really detect it.
WHAT ARE THE MOST USED FILE FORMATS FOR COLORING PAGES?
PDF – Portable Document Format
This is a lossless file format.
There are a number of ways to view PDF-files, even if you don’t have Adobe Acrobat Reader. But since it’s free, you might as well install it on your computer. Here’s a link to Adobe Acrobat Reader.
PDF-files work for both digital and traditional coloring.
JPG (also known as JPEG) – Joint Photographic Experts Group
This is a lossy file format.
Like I mentioned earlier; you usually can’t tell that there’s been a quality reduction. Lots of coloring page creators sell their work as JPG-files, and the quality looks perfectly fine.
The problem arises if you repeatedly edit and re-save the same JPG-file, because then you put the image through the same lossy compression again and again, resulting in lowered quality for each re-save.
JPG-files work for both digital and traditional coloring.
PNG – Portable Network Graphics
This is a lossless file format.
PNG-files can be printed for traditional coloring, but this file format was specifically developed for digital use. PNG-files are great for digital coloring because they can be saved with a transparent background, which for instance makes it super easy to change the color on the line art.
