Problems with transformation tool

Hi everyone, I’m Cintia and I’m beginner using Krita. Recently, I have a problem with transformation tool, when I scale an image, it lose a lot of quality, and it’s images of 300pp, so I don’t know why lose so much quality.
I put an example with my own illustration, the first one is unscaled and the other, scaled.


I don’t think that this was normal, so for that reason I’m asking for help. This isn’t the only problem, because the other tools of transformation, such as free transformation, perspective… it lose quality too when I applied at some part of my draw. I have tried to change the filter, with nearest neighbor I have the best results, but, even so, you notice that the line loses quality.

I’ll wait for some help, thanks for all!!

Hello and welcome to the forum :slight_smile:

All digital ‘painting’ applications use a grid of pixels to present an image and this limits the possible resolution of the image.

The ppi (pixels per inch) number only has use or meaning for printing images. What matters for resolution and detail is the size of the image in pixels.

When you scale an image down you lose pixels and so you lose resolution:

You’re trying to represent the same image using fewer pixels and so the resloution and ‘quality’ is reduced:

Any transform produces a new representation by arithmetic/mathematical methods and may or may not look ‘good’ depending on what the image is and how you judge ‘quality’.

Thaks for answer me.
The resolution of this illustration is 2480x3508 pixels. And other images that I used it’s with a similar size and always lose a lot of quality. I have tried to scale the same image with other application (autodesk skeetchbook) and with this program I don’t have this problem, so I understand that is some kind of krita’s problem or that there is something that I do not do well.

Hi

Which algorithm do you use with transformation tool?

Grum999

I use the command CTRL + T, then I choose the option free transformation, and then I scaled the image


In tools options, you can see which algorithm (filter) is applied

You reduce or increase size?

For example, the “nearest neighbor” is not recommended (no antialiasing)
After you can test with “bicubic” or “Lanczos3” for example (the first one will give soft/blurry interpolatio, the second one will be more sharp…)

Grum999

Ah ok. I’ve tested with all the filters, and nothing, when I applied the nex scale, the quality is reduced, and the image shows this pixels.



The green arrow represent 100pixels on screen
The red arrow represent 100pixels on your drawing

You’re actually giving an example where you’ve made a zoom at ~570% I think
With a such zoom level, pixels are visible

Can you provide full screenshot (with status bar)?

Looking your initial post, this:
image
is typical from a “nearest neighbor” algorithm

Looking the last example you provided, with mlanczos3 algorithm:

Result is normal(antialiased)

Can you tell us:

  • original image size
  • final resized size

Concerning other software on which problem doesn’t occurs, I’m curious: can you provide an example on which everything is fine after rezising?
It could help to understand what’s wrong

Grum999


here is the fullscreenshot with the status bar.

The original image size is 2480x3508
and the final resized image size is 1080x1080 pixels, i’m resized to this size just as a way of doing an example for what it’s happening always that I tried to scaled an image.

When I rezise the same image (2480x3508) to 1080x1080 in Autodesk Sketchbook this is the result

It looks like autodesk sketchbook is applying a trilinear filtering (or a filter like that) in zoom mode, that’s a thing Krita fortunately doesn’t.

Here someone complaining about this zoom filter applied in autodesk sketchbook

To check my idea, can you:

  1. Save this picture:
    image
  2. Open it in Krita and zoom at 800%
    You should get something like this (pixels are properly visible)
  3. Open it in Autodesk Sketchbook and zoom at 800%
    You should get something like this (pixels are smoothed):

If you can post here screenshot of autodesk sketchbook result of this test :slight_smile:

Grum999

You can also check settings of Autodesk sketchbook
http://help.autodesk.com/view/SKETPRO/ENU/?guid=SKETPRO_Help_sb_preferences_html#preferences-in-sketchbook-for-windows-10

then enable Pixel Preview. To change your view back, turn Pixel Preview off.

What is current settings in autodesk sketchbook?
If you switch it to “ON”, does the result in zooming is the same than in Krita?

Grum999

Actually, it does. You can select High Quality (our own shaders), trilinear, bilinear and Nearest Neighbour in the display settings.

Yes, but it’s applied on surface pixel level, not on image pixel level.

Grum999

Honestly zooming in 500% and complaining about pixels is like getting nose close to a van gogh and complaining about it’s grainyness :sweat_smile:

No one will look at an artwork like this. How it looks in 100% is what counts.

Yes, the results of my screenshots is exactly like yours.

So the conclussions that I extract from this is that the resized is correctly, but I’m lose quality anyways? Because I’m using 400% zooming and this It will be noticed always. The doubt that I had, and for wich it was so strange to me was that when I resized an image of 2480x3508 lose so much quality by converting it into a smaller size.

Ok my though was right :slight_smile:
Did you try to activate Pixel Preview option to see if result is the same than in Krita?

When you resize an image, as @AhabGreybeard explained in his post, you loose pixels (if you reduce size)

When you zoom at 400%, each pixel is rendered on screen with 4pixels width square, so you see heavily the pixels.
By default when zooming with autodesk sketchbook, it try to extrapolate these 4pixels size square, building new pixels (this is what I did with Krita in my 2nd example, I resized image at 80% with a “bell” interpolation-that’s like bicubic or trilinear interplation, a method to add pixels to sooth results)

Applying a filter when zooming in could be a good idea on a gallery software, but not on an editing/painting software because you won’t really see what you have in your image.

Convert it to 100x100 pixels size to compare :slight_smile:

Is there a reason to use a 400% zooming?

Grum999

Is there a reason to use a 400% zooming?

No, there is no reason only for compare…

So thanks a lot for your help, It has helped me a lot to understand what happen and undertand some concepts :grinning:

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