Modern reading systems include features to zoom into images using a dedicated viewer. To ensure this feature is effective, images must have sufficient resolution for clarity without unnecessarily increasing the ebook’s file size. It is also important to consult distributor specifications, which may include specific requirements.

Objectives

• Reduce data download requirements.
• Improve page rendering speed.
• Decrease the energy footprint of digital reading.
• Provide flexibility for viewing and zooming images.
• Ensure performance and compatibility across various reading systems.

Implementation

• Optimize images by selecting appropriate resolutions (typically 72 to 150 DPI) and formats (JPEG for photos, PNG for transparency, SVG for vector graphics).
• Use compression tools to reduce file size without perceptible loss of quality.
• Review distributor specifications to comply with their specific technical requirements.

Control

• Check that images display and zoom smoothly across multiple reading systems, targeting a maximum zoom level of at least 200%.