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Osclass

Configuring Image Sizes and Formats

Osclass allows administrators to define image sizes, formats, and processing methods to optimize the visual presentation of listings while ensuring efficient resource usage.

Image Sizes

When a user uploads an image to a listing, Osclass generates multiple versions of the image:

  • Thumbnail: Typically used on homepage, search results, or as small thumbnails on item pages. Default size: 240x200px.
  • Preview: Used in listing page galleries or larger images for search results.
  • Normal: Large showcase image displayed on the item detail page. Default size: 640x480px.
  • Original: A copy of the uploaded image without any modifications. Enabling this option increases storage usage.

These sizes can be configured in Settings > Media within the backoffice.

Image sizes
Image sizes

Image Format and Ratio

Osclass provides advanced settings to control how images are processed:

Force JPEG

Converts all uploaded images to JPG/JPEG format. PNG images with transparency will be converted to PNG with a white background.

Crop Image

Automatically detects the best crop for images, ensuring no white spaces are left. Best used when uploaded images have similar aspect ratios.

Force Aspect Ratio

Maintains the original aspect ratio of uploaded images instead of scaling to predefined dimensions. This ensures image proportions are preserved but may cause irregular thumbnail sizes.

Example:
User uploads an image of 2000x1000px (aspect ratio 2:1) and the configured thumbnail size is 240x200px.
With aspect ratio enforcement, Osclass will generate a 240x120px thumbnail instead of stretching it to 240x200px.

Maximum Image Size

Defines the maximum file size (in KB) for uploaded images. Recommended range: 4000KB - 16000KB. Keeping original images enabled may significantly increase disk usage.

Image Processing Library

Osclass supports two image processing libraries:

  • GD Library: Default image processor with basic functionality.
  • ImageMagick: More efficient and recommended when available. Can handle larger images with lower memory usage.

If ImageMagick is unavailable, contact your hosting provider to enable it.

Canvas Background

Defines the background color used when resizing images. It has no effect when Force Aspect Ratio or Best Crop options are enabled.

  • Most sites should use white as the background.
  • Set to black if required for theme consistency.

Watermark

Osclass allows adding watermarks to generated images to protect content. Watermarks can be:

  • Text-based: Overlays text on images.
  • Image-based: Uses a transparent image (e.g., PNG) as a watermark.

Note: Watermarks do not apply to original images. If the original image is displayed on listings, watermarks will not be visible.

Regenerating Images

When changing image sizes or settings, existing images need to be regenerated. The Regenerate Images tool ensures all images comply with new settings.

Warning:
- Regeneration is resource-intensive; increase PHP memory_limit and max_execution_time before starting.
- If "Keep Original Images" is enabled, regeneration maintains high image quality.
- Without original images, regeneration uses normal-sized images, potentially reducing quality.

Best Practices for Regeneration

  • Increase memory_limit in PHP to 256MB+.
  • Set max_execution_time to 600s to prevent timeout issues.
  • Newer Osclass versions pause regeneration before timeout, allowing continuation from the last processed image.

Once image settings are configured, save changes before regenerating images to avoid inconsistencies.