Before I start, I’ll repeat again, I’m using GIMP for this tutorial, a free image manipulation software, you can download it at: http://www.gimp.org/downloads/
So, let’s say I have a photo I wish to print on a white shirt, it’ll look like this,
Of course, you can just use this image without further adjustments, but it’s gonna look like a slab of sticker just stuck to your shirt – because of the border.
GIMP has a function which let you blur the border, to look like this,
For this, I selected: Filter > Decor > Fuzzy Border,
I chose the highest granularity, you can experiment with lower granularity‌
The color lets you choose the border color, you can try different colors and check the effect, Border size lets you determine how far into the image do you want your border to be, I use border size 55, Add shadow lets you add a dark shade around your border, you can try it out. I will not show every single effect, because if I put too many images in this file, it’s gonna slow down the loading time. Since you already know the function, you can try it out ☺. Hint: you might not want to put a too high value for ‘Add shadow’ because it’ll enhance your border lines.