Most theme images are low-res, there really is no such thing as "hi-res" graphics in a theme. Most theme's are around 2MB when zipped and there are hundreds of images, think about that math.
You really can't judge if there's something wrong with a particular image by posting a screen shot since there's a combination of items to consider.
What most often makes images look blurry within a theme is that the image's resolution is one dimension and the scaling of that image is something different than the image's native resolution within the rtconfig.txt file.
For example, if the image's actual resolution is 20x20 pixels, and the size of that image is set to 21x20 pixels inside of the rtconfig.txt file, then Reaper needs to stretch that original 20x20 image into the defined 21x20 size and in most cases the image will appear blurry/distorted when viewed in the theme. If you grabbed that knob stack from another theme and threw it into your theme, set the size within the rtconfig to your preferred size and expected it to look clear within the theme without making any modifications to the image, that is where you went wrong.
That's where you would start to troubleshoot blurry images. Look at the image's actual resolution and then go into the rtconfig and see if it is a different size.
There are some exceptions to this rule through the use of pink/yellow lines but in most instances when it's a knob such as you posted, this general rule applies.
To fix this you either need to change the size in the rtconfig file or modify the image so it matches what is in the rtconfig. The bottom line is for best viewing experience it is a good practice to set them to match. Then after doing that and if it still looks blurry, then you can focus on the image quality of the actual image file.
low res png knobs
Linear Mode
