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Image Filters ​

Skymage provides a set of image filters that allow you to apply creative effects to your images. These filters can dramatically change the look and feel of images with a simple URL parameter.

Basic Usage ​

To apply a filter to an image, add the filt parameter to your image URL:

https://demo.skymage.net/v1/daudau.cc/images/crab.png?filt=grayscale

Grayscale filter example

Available Filters ​

Skymage currently supports three filter types:

Grayscale ​

Converts the image to black and white (grayscale).

https://demo.skymage.net/v1/daudau.cc/images/crab.png?filt=grayscale

Grayscale filter example

Sepia ​

Applies a warm brown tone to create a vintage or antique look.

https://demo.skymage.net/v1/daudau.cc/images/crab.png?filt=sepia

Sepia filter example

Negative ​

Inverts all colors in the image, creating a negative/inverted effect.

https://demo.skymage.net/v1/daudau.cc/images/crab.png?filt=negate

Negative filter example

Brightness ​

Adjusts the brightness of an image using the bri parameter. This can make images lighter or darker.

https://demo.skymage.net/v1/daudau.cc/images/crab.png?bri=69

Increased brightness example

The bri parameter accepts values from -100 (completely darkened) to 100 (maximum brightness):

  • Negative values (-100 to -1): Decrease brightness (darken the image)
  • Zero (0): No change (original brightness)
  • Positive values (1 to 100): Increase brightness (lighten the image)

Examples:

Darkened Image (bri=-50):

https://demo.skymage.net/v1/daudau.cc/images/crab.png?bri=-50

Decreased brightness example

Brightened Image (bri=50):

https://demo.skymage.net/v1/daudau.cc/images/crab.png?bri=50

Increased brightness example

Contrast ​

Adjusts the contrast of an image using the con parameter. This affects the difference between dark and light areas.

https://demo.skymage.net/v1/daudau.cc/images/crab.png?con=50

Increased contrast example

The con parameter accepts values from -100 (minimum contrast) to 100 (maximum contrast):

  • Negative values (-100 to -1): Decrease contrast (flatten the image)
  • Zero (0): No change (original contrast)
  • Positive values (1 to 100): Increase contrast (enhance differences between dark and light)

Examples:

Reduced Contrast (con=-50):

https://demo.skymage.net/v1/daudau.cc/images/crab.png?con=-50

Decreased contrast example

Enhanced Contrast (con=50):

https://demo.skymage.net/v1/daudau.cc/images/crab.png?con=50

Increased contrast example

Combining Brightness and Contrast ​

For more control over image appearance, you can combine brightness and contrast adjustments:

https://demo.skymage.net/v1/daudau.cc/images/crab.png?bri=20&con=30

Combined brightness and contrast

Common Use Cases ​

Grayscale ​

  • Professional Photography: Create timeless, classic images
  • Print Materials: Prepare images for black and white printing
  • Reducing Visual Noise: Remove color distractions for UI elements
  • Accessibility: Improve readability for color-blind users

Sepia ​

  • Vintage Effect: Create nostalgic, old-time photos
  • Warming Cold Images: Add warmth to sterile or cold-colored photos
  • Thematic Consistency: Create a consistent historical theme across different images
  • Brand Styling: Apply consistent warm tones for brand identity

Negative ​

  • Artistic Effects: Create surreal or abstract visuals
  • Analysis: Highlight certain details that may be difficult to see in normal images
  • Visual Interest: Create striking, unusual versions of common images
  • Dark Mode Inversion: Generate inverted versions of icons or graphics

Brightness Adjustment ​

  • Correct Underexposed Images: Brighten photos taken in low light conditions
  • Create High-Key Images: Create bright, airy aesthetics for fashion or product photography
  • Visual Hierarchy: Make key elements stand out by increasing their brightness
  • Dark Mode Adaptations: Create lighter versions of images for dark mode interfaces

Contrast Adjustment ​

  • Enhance Flat Images: Improve impact by adding contrast to hazy or flat images
  • Text Legibility: Increase contrast to make text stand out against backgrounds
  • Artistic Effects: Create dramatic high-contrast images for visual impact
  • Weather Conditions: Correct for fog or mist that reduces natural contrast

Best Practices ​

  • Consider the purpose of your image when choosing a filter
  • Use filters consistently across related images for cohesive design
  • Consider combining filters with other effects like blur or sharpening for more complex visual styles
  • Test filtered images across different devices to ensure the effect works as expected
  • Filters are applied on-demand and may slightly increase processing time for very large images
  • When adjusting brightness, check for detail loss in highlights and shadows
  • Apply contrast adjustments after brightness changes for more control
  • For printable images, slightly higher contrast often produces better results
  • Consider the viewing environment — higher contrast for bright environments, lower for dim settings

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