Understanding Digital Images & Pixels

• Digital images are composed of picture elements called pixels
• Digital images are digitised and turned into a sequence of numbers computers can understand

Extension: Picture Elements

• Picture elements, also known as pixels, are the smallest discrete component of an image
• Pixels are typically a colored dot on a CRT screen

Digital Images

• Digital images are visual representations stored in a digital format
• Digital images are captured and stored electronically, making them easier to edit, share, and reproduce, unlike traditional film-based images.
• Digital images comprise pixels, which contain color and intensity information to display the image on screens or print it

Pixel

• A pixel is short for picture element and is a tiny square of color
• A digital image can be formed when many pixels come together

Types of Digital Images

• Bitmap images store images using pixels and store the information as a map
• Vector graphics are made of lines, curves, and shapes instead of pixels, each part is editable and easily resized
• Vector graphics are great for diagrams or graphics, but not photographic images

Vector Images

• Vector images are created using mathematical formulas that define shapes like lines, curves, and polygons
• Common file formats are SVG (Scalable Vector Graphics), AI (Adobe Illustrator), and EPS (Encapsulated PostScript)

Bitmap Images

• Bitmap Images, also known as raster images, are made of a grid of individual pixels and that make the complete image
• Bitmap images are resolution-dependent, meaning their number of pixels per inch (PPI) or dots per inch (DPI) determine their quality
• Common file formats include JPEG, PNG, GIF, and TIFF

Image Resolution

• Image resolution is typically described in PPI, or pixels per inch
• Higher resolutions result in more pixels per inch, resulting in more pixel information and a high-quality, crisp image
• Images with lower resolutions have fewer pixels, and the picture becomes distorted if stretched

Image Metadata

• Image metadata is data about data that describes and contextualizes it and it helps to organize, find, and understand data.
• Typical metadata includes title, description, tags, categories, creator, creation date, modification date, and access permissions

Storage Units

• Bit: 1 or 0, a single pixel in black and white
• Byte: 8 bits, a character
• Kilobyte: 1024 bytes, a small email
• Megabyte: 1024 kilobytes, 1 megabyte of MP3 files per minute
• Gigabyte: 1024 megabytes, 300 MP3 songs
• Terabyte: 1024 gigabytes, about 100 DVD-quality films
• Petabyte: 1024 terabytes, enough MP3 songs to play continuously for over 2000 years without repeating

Calculating Image Size

• To calculate image size:
• Multiply the width and height of the image, in pixels, to get the total pixel count.
• Multiply the total pixel count by 3 to get the image size in bytes.
• Divide the number of bytes by 1024 to get the image size in kilobytes.
• Divide the number of kilobytes by 1024 to get the image size in megabytes.

Image Compression

• It is possible to compress or squeeze an image to reduce its file size which will take up less room on your computer.
• There are two types of compression: lossy and lossless

Lossless Compression

• Lossless compression rewrites data for more efficient storage, while maintaining the file quality (e.g., BMP, PNG)

Lossy Compression

• Lossy compression removes some data, reducing the file quality (e.g., JPEG, GIF)

Lossy File Formats

• JPEG (Joint Photographic Experts Group)
• MP3 (MPEG-1 Audio Layer 3)
• AAC (Advanced Audio Coding): AAC is a lossy audio file format commonly used for compressing audio files
• AAC provides better sound quality compared to MP3 at the same bitrate, making it popular for streaming and digital audio applications

Lossless File Formats

• PNG (Portable Network Graphics)
• FLAC (Free Lossless Audio Codec): FLAC is a lossless audio file format that compresses audio files without losing audio quality
• TIFF (Tagged Image File Format): It is commonly used in professional settings, such as graphic design, printing, and archival purposes

Image File Formats

• Photoshop (.PSD): A proprietary format. Stores transparency, layer information, and vector objects (e.g., text)
• Tagged Image File Format (.TIFF): Uncompressed TIFFs suit storing high-quality images and are recognized by many graphics packages and operating systems and they can also support layers, transparency, and vector objects.
• Bitmap (.BMP): A Windows OS image format, not a good choice unless the image is being used by Windows OS
• Joint Photographic Expert Group (.JPG): A compressed format ideal for photographic images, but not suitable for images with flat color
• Graphics Interchange Format (.GIF): Another compressed format, GIF is good for logos with flat areas of color/line-art but not suitable for photographic images, it supports transparency and animation.
• Portable Network Graphics (.PNG): A relatively new format suitable for both photographic and flat images. not all features

What is Photoshop?

• Adobe Photoshop is a software application for image editing and photo retouching on Windows and macOS computers
• Photoshop enables users to create, enhance, and edit images, artwork, and illustrations
• Adobe Photoshop can change backgrounds, simulate real-life paintings, and create alternate views of the universe

What is Pixlr?

• Pixlr is a web-based image editing tool that offers features to edit and enhance digital images

Key Features of Pixlr

• Image Editing Tools: Pixlr offers tools for editing and enhancing images, including cropping, resizing, rotating, brightness, contrast, saturation adjustment, red-eye removal, and spot healing
• Layers and Masks: Pixlr supports layers for working on different image elements separately
• Masking tools enable selective adjustments and blending of different layers
• Filters and Effects: Pixlr offers filters and effects for creative image enhancements like style, textures, and overlays
• Creating different artistic looks or emulating photographic effects
• Text and Graphics: Pixlr users can add and customize text overlays and graphic elements, and access a library of pre-designed stickers, icons, and decorative elements
• Collage and Templates: Pixlr allows users to create collages by combining multiple images into a single composition with templates and layouts for quick, visually appealing collages
• Browser-Based and Mobile-Friendly: Pixlr operates within a web browser and is compatible with mobile devices for on-the-go image editing

Applications of Pixlr

• Photo editing
• Graphic design and illustration
• Social media content creation
• Collage creation
• Photographers
• Education and creative projects

Pixlr Elements

• Commonly used capabilities include:
• Manipulating an image's color
• Cropping images
• Repairing flaws like dust on the lens or red eyes
• Drawing on an image with a pen or pencil
• Adding text to images
• Removing people or objects within an image
• Organizing photos for quick access
• Publishing images online or via email

Advantages of Pixlr

• Accessibility: Pixlr is a web-based application that can be accessed directly via a web browser without downloads or installation.
• User-Friendly Interface: Pixlr provides an intuitive and easy-to-navigate interface.
• Extensive Editing Features: Pixlr offers cropping, resizing, rotating, and color/exposure adjustment.
• Template Library: Pixlr's library offers pre-designed templates such as social media graphics, posters, and banners that serve as starting points.
• Collaboration and Sharing: Pixlr enables easy collaboration and sharing of edited images with cloud saving, sharing, and real-time collaboration
• Integration with Creative Cloud: Pixlr is part of the Adobe Creative Cloud ecosystem, which enables users to import and export files between Pixlr, Photoshop, and Lightroom

Disadvantages of Pixlr

• Limited Advanced Features: Pixlr may have limitations compared to professional desktop image editing software such as Adobe Photoshop.
• Internet Connection Requirement: As an online tool, Pixlr requires a stable internet connection to access features affecting responsiveness with slow connections
• Less Suitable for Complex Projects: Pixlr may not be suitable for highly complex or professional-level image editing tasks.
• Dependency on the Pixlr Platform: Workflow or access to edited images may be impacted by technical or significant changes to the Pixlr Platform

Pixlr Tools

• Selection tools like Marquee and Wand, Lasso
• Arrange, Crop, Liquify, Clone, Dodge/Burn
• Pen, Eraser, Fill, Shape, Picker, Hand/Pan
• Heal, Blur/Sharpen/Smudge, Sponge/Color, Draw, Color Replace, Gradient, Text, Zoom, Cutout/Mask tools
• Editing Background and Foreground