The ability to create and edit raster graphics is essential for interior design professionals in Kenya to communicate design concepts visually. Raster graphics, composed of pixels, are ideal for detailed images such as photographs and textured surfaces that interior designers frequently incorporate into mood boards, presentations, and client proposals. Mastery of software like Adobe Photoshop enables designers to manipulate images with precision, enhancing realism and appeal of interior design projects. This chapter introduces Photoshop as a powerful tool tailored for interior design applications, focusing on creating and editing raster graphics effectively.

2.1 Introduction to Photoshop

Adobe Photoshop is a professional raster graphics editor used to create, edit, retouch and combine pixel-based images. It was created by brothers Thomas and John Knoll and first released by Adobe in 1990, and it is now delivered as part of Adobe Creative Cloud through a subscription. In interior design, Photoshop is the standard tool for editing site and product photographs, building mood boards, combining furniture and finishes into room images, enhancing 3D renderings and preparing images for presentation boards, print and social media. Its strength lies in non-destructive working with layers, masks and adjustment layers, which allows designers to change images repeatedly without damaging the original. Example: a designer refurbishing a coffee shop photographs the existing space, then uses Photoshop to show the client new wall colours, pendant lights and furniture placed realistically into the photo.

Uses of Photoshop in interior design

Photoshop supports interior designers from the first concept to marketing the finished project. Knowing its main uses helps learners see why the skills in later topics matter. Example: a designer working for a property developer uses Photoshop to produce marketing images of show apartments before construction is complete.

Main uses

• Mood boards and concept boards: Combining images of materials, colours, furniture and inspiration into one visual.
• Photo editing and retouching: Correcting lighting, colour and perspective in photographs of spaces and products.
• Virtual staging: Placing furniture, curtains, rugs and decor into photos of empty or existing rooms.
• Material and colour studies: Testing different paints, fabrics and floor finishes on the same image.
• Rendering post-production: Adding lighting effects, people, plants and atmosphere to 3D renderings.
• Texture preparation: Creating seamless textures of wood, stone or fabric for 3D software.
• Presentation and marketing graphics: Preparing images for boards, brochures, websites and social media.
• Colour-rendered plans: Adding colour, textures and shadows to floor plans exported from CAD.

Key capabilities of Photoshop

Photoshop's features can be grouped into a few core capabilities, each explored in detail in later topics of this chapter. Example: a designer preparing a bedroom visual for a resort uses selections to isolate the bed, layers to try different bedspreads and adjustment layers to warm the lighting.

System requirements

Photoshop handles large, high-resolution images, so it needs a capable computer. Working on an underpowered machine leads to slow performance, crashes and lost work. The exact requirements change with each version, so they should be checked on Adobe's website before buying hardware. Example: a design department at a technical training institute upgrades its laboratory computers' memory and graphics cards so that trainees can edit large rendering files smoothly.

Photoshop and alternative raster editors

Photoshop is the industry standard, but other raster editors are available, some free. Learners should know the alternatives, especially when budgets are limited, while recognising that many employers expect Photoshop skills. Example: a design student practises on a free browser-based editor at home and uses Photoshop in the college laboratory.

Getting started with Photoshop

Starting Photoshop involves installing it through the Creative Cloud desktop app, signing in with an Adobe account, launching the program and creating or opening a document. Setting up a new document correctly avoids having to resize work later. Example: a junior designer at a furniture showroom installs Photoshop and creates an A3 document at 300 ppi for a printed product board.

Steps for installing and launching Photoshop

1. Create an Adobe account: Sign up with an email address on Adobe's website.
2. Choose a plan: Select a Photoshop or Creative Cloud plan, or start a trial where available.
3. Download Creative Cloud: Install the Creative Cloud desktop app.
4. Install Photoshop: Click Install next to Photoshop in the app.
5. Launch Photoshop: Open it from the Creative Cloud app or the Start menu or Applications folder.
6. Sign in if prompted: Confirm the licence with your Adobe account.

Steps for creating a new document

1. Click New file: Or choose File, New, or press Ctrl + N.
2. Choose a preset or enter a size: Select Print, Web or a custom size in millimetres or pixels.
3. Set the resolution: Use 300 ppi for close-viewed print or 72 to 150 ppi for screen.
4. Choose the colour mode: Select RGB for screen work or CMYK where the printer requires it.
5. Set the background: Choose white, black or transparent.
6. Name the document: Type a clear name.
7. Click Create: The new document opens on the canvas.

Worked example: pixel size of an A3 document at 300 ppi

Pixels = size in millimetres ÷ 25.4 × resolution

An A3 page is 297 mm × 420 mm, set at 300 ppi.

Width = 297 ÷ 25.4 × 300 ≈ 3,508 pixels

Height = 420 ÷ 25.4 × 300 ≈ 4,961 pixels

The document is about 3,508 × 4,961 pixels.

Raster and vector images compared

Photoshop works mainly with raster images, so the designer must understand how they differ from the vector graphics produced by programs such as Illustrator or CAD.

• Resolution dependence: A raster image has a fixed number of pixels, so it must be created or captured at the size and resolution of its final use.
• Colour depth: Raster images can hold millions of colours, which is why they show materials and lighting realistically.
• Layer support: Photoshop keeps parts of a raster image on separate layers so they can be edited independently.

Chapter Summary

This chapter provides a comprehensive introduction to Photoshop as a leading software for creating and editing raster graphics. It explores the Photoshop workspace, detailing the layout and tools essential for efficient image manipulation. The concept of an image is examined, focusing on its properties and how digital images are constructed. Image editing techniques are discussed, highlighting methods to enhance and modify pictures for various purposes. The chapter also covers the practical application of Photoshop in real-world projects, emphasizing workflow and creative processes. Instructions on saving and exporting images are included to ensure proper file management and compatibility for different platforms. The production of images is addressed, explaining how to prepare graphics for print and digital use. Finally, the chapter concludes with guidance on presenting images effectively to communicate visual information clearly and professionally.