May 6, 2009

Migrating from Picasa to GIMP

Posted in Misc at 06:07 by Graham King

I’ve been using Picasa to edit my pictures for a long time, and it’s an excellent program. Recently however I’ve started shooting RAW, and I’d like control, so I’ve started using GIMP. It’s more powerful and more complicated than Picasa, so to start myself off I went through all the features of Picasa and made notes on how to duplicate that operation in GIMP. Here are those notes.

Most of what Picasa does can be replicated with the Colors / Levels or Colors / Curves tool. It’s well worth spending a little time experimenting with both of those (the documentation is very good too).

Crop

In the Toolbox, click the Rectangle select tool
In its options (beneath the tools), tick ‘Fixed: Aspect Ratio’
Enter 6:4 ratio (for 1.6 sensor, most DSLRs)
Tick Highlight. Draw a rectangle on the image that you want to crop to.
Image menu / Crop to Selection

Straighten

Click one of the rulers above or to the left of the image, and drag a guideline onto your picture
In the Toolbox, select the rotate tool
Select ‘Clipping: Crop to result’. Maybe ‘Interpolation: Sinc (Lanczos3)’, although that doesn’t seem to matter
Rotate until your picture is straight, using your guideline
Click Rotate
Image / Fit Canvas to Layers or Image / Autocrop Image
Image / Guides / Remove all guides

Redeye

Filters / Enhance / Red-Eye Removal (I have never used this)

I’m feeling lucky

Colors / Levels / Auto

Auto Contrast / Auto Color

Colors / Auto / something

Fill light

Colors / Levels
Drag the middle triangle (grey) to the left

Highlights

Colors / Levels
Drag the right side (white) triangle

Shadows

Colors / Levels
Drag the left side (black) triangle

Color Temperature

Tools / GEGL Operation / color-temperature
Adjust Intended Temperature

Neutral Color Picker

Colors / Levels
There are three color pickers near the bottom right
Use the left one to select black, the middle one neutral gray, and the right one white

Sharpen

Filters / Enhance / Unsharp mask
Try these values: Radius: 1 – 5 Amount: 0.5 – 1
OR
Colors / Components / Decompose.
HSV, Decompose to layers
Switch off the hue and saturation layer
Apply the Unsharp mask, as detailed above
Colors / Components / Recompose

Sepia

Filters / Decor / Old Photo

B & W

Image / Mode / Grayscale
OR
Colors / Desaturate

Warmify

Colors / Curves
Select Blue – pull the center-right of the curve down most of a grid box
Select Red – pull the center-right of the curve up most of a grid box
OR Tools / GEGL Operation / color-temperature / Increase intended temperature by 10k or 20k

Saturation

Colors / Hue-Saturation / Pull the Saturation slider to the right

Soft Focus

Duplicate layer (right click / Duplicate or use the icon bottom of layers pane)
Filters / Blur / Gaussian Blur.. Set to 60
Reduce Opacity to ~60%
Right click on blur layer, Add Layer Mask, White (full opacity)
Click the foreground color, set S to 0 and V to 50 (or 60, 70)
Select a brush, the Paintbrush tool, paint over the parts you don’t want fuzzy
To replicate Picasa this would be a big circle somewhere in the middle of the picture

Graduated tint

Duplicate layer
Switch off Background by clicking the eye
Edit that layer with Levels and Curves to expose sky correctly
Right click on new layer / Add Layer Mask/ White (full opacity)
Select Blend tool
Draw a line on the image to make a gradient. Try again.
Click the Background eye back on
Right click on the edited layer, and Apply Layer Mask
Merge the layers