Affinity Photo - Resize image without quality loss

[MepMeeep]

I try to resize an jpeg image. I open it with Affinity Photo and want to create an image size 12x17cm. But when I choose document > resize document and give the new size in px, the image is resize but the quality is very bad. Why does it not resample the image?

[walt.farrell]

14 minutes ago, MepMeeep said:

I try to resize an jpeg image. I open it with Affinity Photo and want to create an image size 12x17cm. But when I choose document > resize document and give the new size in px, the image is resize but the quality is very bad. Why does it not resample the image?

What was the original size in px of your jpeg file, before you did the resize? What resample method did you choose? Can you provide some screenshots?

 

[Fixx]

Probably mixed resampling and resizing and physical size and size in pixels.

[MepMeeep]

from 3024 px x 4032 px and 72dpi to about 12cm width which is 340px x 453 px with resambling bilinear

[JohnZeman]

After you have resized the image did you go to
Menu > View > Zoom > 100%  (CTRL + 1 on Windows)
To show the image at its new full size?

[walt.farrell]

51 minutes ago, MepMeeep said:

from 3024 px x 4032 px and 72dpi to about 12cm width which is 340px x 453 px with resambling bilinear

3024 x 4032 px @ 72dpi would be about 42 x 56 inches (or about 107 x 142 cm).

What you did was to drastically reduce the pixel count. You reduced the total pixel count to about 1% of what it originally was if I've done the arithmetic correctly. That cannot possible maintain the same sharpness.

If you wanted your image to have a 12cm width you could have simply changed the dpi value while keeping the number of pixels constant. A dpi value of 600 would do that. (Or, you could cut the number of pixels in half (approximately 1500 in width) at a dpi of 300.)

[MepMeeep]

@walt.farrell this works. Thanks. But why do I have to do this manually. In photoshop if I resize the image it works automatically?

[Minus44]

52 minutes ago, MepMeeep said:

@walt.farrell this works. Thanks. But why do I have to do this manually. In photoshop if I resize the image it works automatically?

Photoshop isn’t doing this as automatically as you might think. Affinity Photo is managing the image with very similar tools, but you may not be as familiar with them. You simply need to give it the DPI that you want in the final result. If you uncheck a box or two in Photoshop, it would do the same thing.