Chapter 2: Advanced GIMP

Class: X | Subject: Information and Computer Technology

Key Concepts

What is GIMP?

GIMP = GNU Image Manipulation Program
A free, open-source image editing tool covered under the GPL (General Public License)., Provides photo retouching, authoring, and composition., Downloadable from www.gimp.org, Available for GNU/Linux, Windows, and Mac OS X., Default file extension: .xcf

Features of GIMP, Simple paint program, Expert quality photo retouching, Online batch processing system, Mass production image producer, Advanced scripting interface, Supports multiple file formats: GIF, JPEG, TIFF, etc., Load and save animations (frame-as-layer format), Virtually unlimited images can be opened at one time, Cross-platform (Linux, Mac OS, Windows)

Advanced Tools (Toolbox)

Tool	Shortcut	Purpose
Move Tool	M	Move layers, selections, paths, guides, or text
Align Tool	Q	Align image layers with various image objects
Scale Tool	Shift+T	Scale (resize) layers, selections, or paths
Shear Tool	Shift+S	Shift one part of image in one direction and another part in the opposite direction
Perspective Tool	Shift+P	Change the perspective/dimensions of the active layer
Flip Tool	Shift+F	Create a mirror image (horizontal or vertical flip)
Rotate Tool	Shift+R	Rotate layers in different directions (90, 180, 270 degrees)
Blend Tool	L	Fill selected area with a gradient blend of foreground and background colours
Blur/Sharpen Tool	Shift+U	Blur to soften or sharpen to increase contrast
Smudge Tool	S	Smudge colours by mixing with adjacent colours
Dodge/Burn Tool	Shift+D	Dodge lightens colours; Burn darkens colours
Eraser Tool	Shift+E	Erase content on the canvas
Pencil Tool	N	Draw like a real pencil (hard edges)
Paintbrush Tool	P	Draw brush-like strokes (soft edges, fill and outline)

Tool Details

Move Tool: Activated via Tools > Transform Tools > Move, or shortcut M. Options include moving by Layer, Selection, or Path. Holding space bar temporarily activates Move tool.

Align Tool: Activated via Tools > Transform Tools > Align, or Q. Click a layer element to choose it for alignment. Shift+click for multiple layers. Supports alignment to first item, and distribution with offset values.

Scale Tool: Access via Image > Scale Image. Set width and height, choose interpolation method (e.g., Cubic), then click Scale. Note: scaling causes some quality loss.

Shear Tool: Horizontal shearing shifts upper part right and lower part left (or vice versa). Access via Tools > Transform Tools > Shear, or Shift+S.

Perspective Tool: Changes the dimensions of the active layer content, selection, or path. Shows a transformation matrix. Access via Shift+P.

Flip Tool: Creates a mirror image. Access via Tools > Transform Tools > Flip, or Shift+F. Can flip horizontally or vertically.

Rotate Tool: Revolves layers, paths, or selections. Access via Image > Transform > Rotate (90/180/270 degrees).

Blend Tool: Creates gradients by mixing foreground and background colours. Drag cursor to set gradient direction; shorter drag = sharper blend. Access via Tools > Paint Tools > Blend, or L.

Blur/Sharpen Tool: Blur mode blends pixels with neighbours (softens). Sharpen mode increases contrast (over-application produces noise). Ctrl toggles between modes. Access via Shift+U.

Smudge Tool: Takes colour and mixes it with the next colour along the drag path. Ctrl+Shift constrains angle in 15-degree steps. Access via S.

Dodge/Burn Tool: Dodge lightens, Burn darkens. Mode determines which pixel types are affected. Access via Shift+D.

Layers, Each transparency in GIMP is called a layer., Layers are like transparent sheets stacked on top of each other., You can see through transparent areas to the layers below., A new image starts with a single layer.

Layer Operations:

Adding a Layer: Layer menu > New Layer. Choose name, size, and fill type (Foreground, Background, White, Transparency).
Renaming a Layer: Right-click layer > Edit Layer Attributes > type new name.
Deleting a Layer: Select layer > click the bin/trash button at bottom of Layers tab.
Merging Layers: Open images as layers. Right-click > Merge Down (merges with layer below) or Merge Visible (merges all visible layers).
Scaling a Layer: Layer > Scale Layer. Set width, height, and interpolation. Causes quality loss.
Duplicating a Layer: Layer > Duplicate Layer. Creates an identical copy with " copy" appended to the name.

Masking, A Mask shows the full structure of a selection., Provides the ability to interact with the selection in new ways.

Quick Mask mode shows the selection as a translucent screen overlying the image., By default, the mask is shown in red (changeable)., Toggle Quick Mask: Select > Toggle Quick Mask, or Shift+Q.

Editing a Mask:

Go to Channels tab, select "Quick Mask" channel.
Right-click > Edit Channel Attributes.
Change the colour and fill opacity as needed.

Important Definitions

Term	Definition
GIMP	GNU Image Manipulation Program; free, open-source image editor
GPL	General Public License; allows users to access and alter source code
Layer	A transparent sheet in GIMP; allows working on one element without disturbing others
Masking	A technique to show selection structure and create merge effects
Quick Mask	Mode where selection appears as a translucent coloured overlay
Gradient / Blend	A smooth transition between two or more colours
Retouching	Editing/arrangement of pixels using tools like Blur, Sharpen, Smudge, Dodge, Burn
Perspective	Changing the dimensional view of an image

Key Points

GIMP is free and open-source, covered by GPL.
The Align tool aligns image layers using target references (first item, selection, path, etc.).
Scaling an image or layer causes some quality loss.
Shear shifts opposite parts of an image in opposite directions.
The Perspective tool creates 3D-like dimensional views.
Flip creates a mirror image; Rotate spins the image.
Blend tool creates gradients; shorter drag = sharper transition.
In Sharpen mode, over-application produces noise.
Smudge tool mixes colours along the brush path.
Layers allow non-destructive editing of individual elements.
Merge Down merges one layer with the one below; Merge Visible merges all visible layers.
Quick Mask defaults to red; toggle it with Shift+Q.
Default GIMP file extension is .xcf.

Practice Questions

Multiple Choice (selected):

Which tool adds an identical copy of the active layer?, (d) Duplicate Layer
Default mask colour?, (a) Red
Selection shown as translucent screen in which mode?, (b) Quick Mask
Transparent sheets on top of each other are called?, (c) Layers
Default GIMP file extension?, (a) .xcf
GPL stands for?, (d) General Public License
Image quality is lost by?, (a) Scaling
Over-application produces noise in which mode?, (a) Sharpen
Which tool takes colour and mixes it with the next colour?, (d) Smudging

Short Answer:

Name application areas where GIMP can be used.
List all features of GIMP.
What is GPL?
Which tool aligns objects on different layers? Explain its options.
What properties need to be changed while scaling?
Which tool lightens pixels? Which darkens?
Differentiate between Shear and Perspective tool.
How is Blur different from Smudge?
How is flipping different from rotating?
What are Layers? What is their purpose?

Identify the Tool:

Resize layer/image, Scale Tool
Move layers, Move Tool
Align layers with objects, Align Tool
Create mirror image, Flip Tool
Free hand drawings, Pencil Tool
Lighten colour pixels, Dodge Tool
Wet paint effect, Smudge Tool
Shift part of image to a direction, Shear Tool
Apply colours without affecting original, Masking
Remove objects from canvas, Eraser Tool