http://www.plk83.edu.hk/cy/gimp Contents 1. Introduction (Page 1) 2. Understanding the User Interface (Page 1) 3. Image Authoring (Page 2) 4. Photo Retouching (Page 6) Introduction GIMP is a free computer graphics software for image authoring and photo retouching. The software can be downloaded from its official web site http://www.gimp.org. Understanding the User Interface Three windows are provided. 1. Toolbox 2. Image Window 3. Dialogs Window Steps to open the Toolbox window 1. Press Ctrl+B to open the Toolbox window. 2. Enlarge the Toolbox window. 3. Click Windows Dockable Dialogs Tool Options. 4. Drag and drop the Tool Options window inside the Toolbox window. Page 1 of 8
Image Authoring 1. Create a New Image Click File New Specify the image size and click OK. 2. Paint Tools The following Paint Tools can be found in the Toolbox. 3. Pencil Tool The colour, brush style and the size of the pencil can be specified in the Toolbox. To draw a straight line, firstly you have to draw a point. Then holding down the SHIFT key and draw the end point of the line. Press Ctrl+Z to undo the last action. Press Ctrl+Y to redo the last action. Similar settings are provided for Paintbrush, Airbrush and Ink. 4. Eraser Tool The background colour (usually white colour) and the size of the eraser can be specified in the Toolbox. 5. Bucket Fill Tool First select the Foreground colour fill or Pattern fill in the Toolbox. Then click the inside of a closed area. Background colour Page 2 of 8
Activity 1 Explore other Paint Tools (e.g. Bucket Fill) and draw a beautiful birthday cake. (Hint: you can use the Eraser to clean the wrong drawing. You can also undo the last action by pressing Ctrl+Z.) You can Save the picture as the special GIMP format (XCF) or Export it as a common graphics format (e.g. PNG, GIF or JPG). 6. Selection Tools Rectangle Selection Select a rectangular area Ellipse Section Select an elliptical region Fuzzy Selection It is easier to select a region with the same colour Colour Section Select all regions with the same colour Scissors Section Select any region by using the control points You can add to or subtract from current selection by holding the Shift and Ctrl keys respectively. To move the selection, holding the Alt key and drag the selection. More about Selection 7. Floating Selection To move a part of a picture, create a floating selection. Then, move the floating selection to a new position. Finally, anchor the floating layer. Page 3 of 8
8. Blend Tool You can use any Paint Tool to draw within the selection region only. You can select the Foreground and Background colours The given picture can be obtained by using the Blend Tool. Transformation Tools The following Transform Tools can be applied to the selection. 9. Rotate Select the object with any selection tool. Rotate with a suitable angle. Click the Rotate button. 10. Scale Select the object with any selection tool. Drag the corner to resize the objects Click the Scale button. Page 4 of 8
Activity 2 Using the school logo on the web site, create the following picture. (Hint: You should use the Rotate and Scale Tools.) 11. Layers Click Windows Dockable Dialogs Layers. Copy a dog clipart. Click Edit Paste as New Layer. Rename this layer as "Dog". Repeat the above procedures to create another layer for a cat clipart. The pictures in the two layers can be edited independently. Use the Link button to link up two or more layers. Use the Hide/Show button to hide or show a layer. Use the following buttons to manipulate the layers. Activity 3 Read the following page https://www.gimp.org/tutorials/layer_masks/ Download the picture from http://www.plk83.edu.hk/cy/gimp/ Then, produce a black and white background. Page 5 of 8
Photo Retouching 1. Photo Synthesis Use a desert photo as the background. Find a penguin photo and paste it in a new layer. Resize the penguin (with the Scale Tool) and place it at a suitable position. Use the Paths Tool to outline the penguin. You can use Ctrl+Mouse wheel to zoom in or zoom out the picture and then adjust the anchor points precisely. Click "Selection from Path". (Change the Path to Selection.) Click Select Invert. Press the Delete key to remove the background of the penguin. (Alternatively, you can use the Selection Tools to select the penguin.) 2. Resize the image Click Image Scale Image. Change the Image Size. Click the Scale button. Page 6 of 8
3. Reduce the file size of digital photo Click File Export Input the file name and choose JPEG image type. Click the Export button. Choose a lower Quality and click the Export button. 4. Crop the image Method 1 (remove empty border from the image) Click Image Autocrop Image. Method 2 (crop the image to the extends of the selection) Select a region with the Selection Tool. Click Image Crop to Selection. 5. Red Eye Removal Click Filters Enhance Red Eye Removal Click the Zoom in button to see the red eyes clearly. Choose a suitable Threshold value such that the red eyes can be removed. Click the OK button. Page 7 of 8
6. Change the hair colour Select the hair. Click Colors Color Balance. Adjust the three Color Levels. You can try Shadows, Midtones and Highlights to get different effects. Click the OK button. You can use this method to change the colour of different parts of an image. 7. Change the Brightness and Contrast The face is dark because the given photo is taken with a very bright background. Click Colors Brightness-Contrast It is difficult to get a good result when changing the whole photo. You should select the boy and then adjust the brightness and contrast of this selection only. 8. Improve the skin quality See the tutorial video in http://www.youtube.com/watch?v=fhu-ao24lxo. (You only need to see the first 3 minutes.) Activity 4 Use the photo retouching techniques to improve your photo. You should also show the original photo. Reference http://gimpbasic.blogspot.hk/ Page 8 of 8