Image File Formats: Advantages and Limitations

Image File Formats

Introduction

  • Pixel-based images can be saved in various file formats, some of which have become industry standards.
  • These formats differ in the color modes they support and the features they offer.
  • Common image file formats include JPEG, PNG, GIF, EPS, BMP, TIFF, PSD, and PDF.
  • Some formats are specific to Macintosh or Windows, while TIFF and EPS are commonly used in graphic production.

Joint Photographic Experts Group (JPEG)

  • Advantage: Same on all company platforms.
  • Limitation: Uses lossy compression, which results in loss of detail and information during conversion. Repeated loading and saving can further degrade image quality.

Portable Network Graphics (PNG)

  • Created as an improvement over the GIF format.
  • Saves transparent pixels using alpha transparency, which offers 256 levels of opacity (from fully transparent to fully opaque).
    • Alpha transparency provides a gradient of transparency levels, unlike simple binary transparency.
  • Advantages:
    • Widely accepted format.
    • Uses lossless compression (no data loss).
    • Supports transparency.
  • Disadvantages:
    • Lossless compression only.
    • Poor compression for photographic images.
    • Does not support animations.

Graphic Interchange Format (GIF)

  • Advantages:
    • Supports simple animations in a single file by displaying multiple images sequentially.
    • Supports transparency.
  • Disadvantages:
    • Larger file sizes compared to JPG or PNG, which can be problematic for internet uploads.
    • Limited to 256 colors (8-bit).

Encapsulated PostScript (EPS)

  • Handles both object graphics and pixel graphics; used with Adobe Illustrator and Adobe Photoshop.
  • Advantages (for pixel graphics):
    • Images can be selected with mask channels.
    • Can store information about halftone screen type, screen frequency, and transfer functions for print adjustments.
  • Consists of a low-resolution preview image (PICT) and a PostScript-based image containing both objects and pixels.
  • The preview image is used when placing the image in page layout software.
  • EPS file formats differ between Windows and Macintosh.
  • The high-resolution pixel part of an EPS file can be JPEG-compressed without losing EPS functionality.
  • PostScript code is encapsulated, providing a degree of protection.
  • Handles line, grayscale, RGB, and CMYK images, as well as object graphics.
  • Limitations:
    • Requires Adobe products and PostScript printers.
    • Not easily accessible to beginners in desktop publishing.
    • If the computer doesn't support PostScript, the monitor display quality may not match the final printed output.
EPS Summary
  • Advantages:
    • Can make selections with channels.
    • Can be stored with information about halftone screens and print prerequisites (color).
    • Safe due to encapsulation.
    • Can be JPEG-compressed.
  • Limitations:
    • Cannot be modified in page layout software.
    • File size is slightly larger than TIFF.

Microsoft Windows Bitmap (BMP)

  • Advantage: Provides a realistic display of the picture, creating the illusion of one color blending into another.
  • Disadvantage: Images tend to lose clarity when resized, and enlargement causes pixelation.

Tagged Image File Format (TIFF)

  • An open image format for pixel-based images.
  • Consists of a file header and information describing the image content, size, and instructions for opening the image.
  • Advantages:
    • Can be LZW-compressed directly from Photoshop.
    • Handles line and grayscale images in RGB and CMYK modes.
  • The TIFF format differs between Windows and Macintosh.
  • Disadvantage: Large file size (can be 100MB or more), making it difficult to transfer via the internet or email.
TIFF Summary
  • Advantages:
    • Color, contrast, and brightness can be modified in page layout software.
    • Can be LZW-compressed.
    • Can be stored with information about print prerequisites (color).
    • Slightly smaller file size than EPS.
  • Limitations:
    • Cannot contain mask channels or halftone screen information.

Photoshop (PSD)

  • Primarily used during image editing.
  • Limitations:
    • Cannot be used for output.
    • Large file size.
  • Advantages:
    • Can save images in layers, allowing for more creativity in image retouching.
    • Many other programs can read Photoshop-formatted files.

Adobe Illustrator (AI)

  • A widely used drawing application.
  • AI is the file extension automatically added when saving a file created in the application.
  • Advantages:
    • Provides creative freedom to realize ideas quickly and powerfully.
    • Allows instant conversion of bitmaps to vector artworks and intuitive painting.
    • Tight integration with other software for producing graphics for print, video, web, and mobile devices.
  • Adobe Illustrator and Macromedia Freehand convert pixel graphics to object graphics.

Macromedia Freehand (FH)

  • A powerful application for creative projects for print or the web.
  • FH is the file extension automatically added when saving a file created in the application.
  • Freehand is a tool for graphic projects and ideas.
  • Examples: Drawing logos, creating business cards and letterheads, storyboarding websites, and creating Macromedia Flash presentations.
  • Freehand has better drawing tools compared to Macromedia Flash, making them a commanding set of tools when used together.

Portable Document Format (PDF)

  • Manages both object graphics and pixel graphics.
  • Adobe Photoshop and Adobe Illustrator can save and edit images in high-resolution PDF.
  • Combines the characteristics of the EPS format and Photoshop, is better standardized, and can be read across all platforms.
  • Advantage: Provides a convenient way to deliver print documents.
  • Disadvantages:
    • Can be slower to download than HTML.
    • Requires the Adobe Reader plug-in to be installed.

Pros and Cons of Different Image Formats

  • Summary of advantages (Pros) and limitations (Cons) for JPEG, PNG, GIF, BMP, TIFF, EPS, PSD, and PDF formats.
JPEG
  • Pros: Small file size, widely supported format, compatibility, good color range.
  • Cons: Lossy compression, not great for text, simple graphics, or illustrations.
PNG
  • Pros: Widely accepted format, lossless, transparency support.
  • Cons: Lossless only, poor compression for photographic images.
GIF
  • Pros: Simple animations/short video clips, widely supported format, transparency support.
  • Cons: Limited to 256 colors (8-bit per pixel), only binary transparency.
BMP
  • Pros: Lossless compression, smaller file sizes, fast to encode.
  • Cons: Large File size.
TIFF
  • Pros: Lossless, high-quality images, compatible with both PCs and Macs, multiple images and multiple pages can be saved in one file.
  • Cons: Large file size Not great for web graphics.
EPS
  • Pros: Scalable to any size, Lossless, Compatibility for vector graphics, Ideal for printing / output.
  • Cons: Minor software compatibility issues, May lose control of advanced vector editing features.
PSD
  • Pros: Lossless, Layers support, Transparency support.
  • Cons: Longer browser loading times., Non-editable content.
PDF
  • Pros: Lossless, Protects intellectual property, Maintains printed format.
  • Cons: Not great for complex graphics printing, Not really useful as a graphic image