Showfoto/Levels Adjust/da

KDE fotointroduktion 1-1 Niveaujustering

Unai Garro (uga) - sommeren 2008

Note

Det originale billede, som bruges i denne vejledning kan hentes her.

Dette er nok en af de mest almindeligt brugte metoder til at justere et billede. Den er så enkel og effektiv, at du nok vil bruge den på alle dine billeder fra nu af, så følg med og god fornøjelse.

Lad os se på dette eksempelbillede fra Akademy 2008, venligst doneret af Sebastian Kügler:

Du bemærker, at fotoet er ret mørkt. Det er taget under en præsentation, så rummet var nok ret mørkt; men det er ingen undskyldning for et dårligt foto

Hvorfor er det mørkt? Lad os åbne fotoet i Showfoto (Digikams redigeringsdel) og se, hvad der foregår:

Øverst til højre ser du billedets histogram. (Jeg har klikket på knappen Lineær over histogrammet til venstre for at se det mere tydeligt). Hvad fortæller histogrammet dig så? Histogrammer tæller blot pixels. Det angiver, hvor mange pixels der er for hvert gråniveau og viser dem i grafen. Til venstre i diagrammet er de mørke farver og til højre de lyse.

You can see that our image has the histogram concentrated on the left part. Thus, it's mostly black. The right part of the histogram isn't used at all, as shown in the figure. Why did this happen? Just because the camera failed exposing the image properly, or was inappropriately configured.

If a photo is visually pleasing, usually (not always), it covers most of the histogram, from black, to white.

So, is there a way to fix this, then? Of course there is, and it's a very easy one. Select the menu Color -> Levels Adjust:

You will see a new popup showing a tool to adjust the histogram output. There are several parts in it. On the top right, there are two histograms. The first one is the output/new histogram, and the second (bottom) one is the input/original histogram.

As you can see, I have adjusted the output histogram to cover it all, see? So how have I done this? Very simple:

There are 4 sliders in this tool. The first two sliders mark the beginning and end of the part of the histogram that I am interested in. I have moved them to match the full histogram of our original image.

The other two sliders mark the range of the histogram we want as output. We want the histogram to cover from black to white, so just move the sliders to the left corner and to the right corner.

Press OK, et voilà, your nice photo is fixed. Congrats