Image Optimisation Guide
PixelTamp utilises embedded native frameworks (ImageIO, CoreGraphics) and the embedded libwebp C library to deliver dramatic file size savings while preserving crisp visual detail.
Supported Image Formats
| Format | Optimisation Method | Key Benefits |
|---|---|---|
| JPEG / JPG | Apple ImageIO colour sharing + lossy quantization |
Strips superfluous metadata, applies progressive encoding, tuned chroma subsampling. |
| PNG | Embedded 8-bit Quantizer with Floyd-Steinberg error diffusion |
Reduces 24/32-bit PNGs to compact 8-bit indexed palettes while maintaining alpha transparency. |
| WebP | In-process Google libwebp encoding |
Produces ultra-compact images with superior compression ratios for modern web browsers. |
| GIF | Frame-by-frame palette reduction or MP4 transcoding | Minimises frame delta sizes or converts multi-megabyte GIFs into lightweight MP4 videos. |
| HEIC / HEIF | Native CoreImage / ImageIO decoding | Seamlessly ingests iPhone and modern camera photos and outputs web-compatible formats. |
PNG Quantisation & Dithering
PNG files often contain 24-bit colour depth and an 8-bit alpha channel, resulting in hefty file sizes. PixelTamp features an embedded palette quantiser:
- Median Cut Colour Reduction: Intelligently selects the 256 most representative colours in the image.
- Floyd-Steinberg Error Diffusion: Smooths gradients and prevents colour banding across photos and complex illustrations.
- Alpha Channel Preservation: Fully supports 8-bit transparent and semi-transparent pixels.
EXIF Orientation Normalisation
Digital cameras and smartphones write orientation metadata (EXIF tags 2 through 8) rather than physically rotating the pixel buffer. When stripping metadata for web privacy and byte reduction, other tools often render photos sideways or upside down.
PixelTamp automatically:
- Detects EXIF orientation tags during ingestion.
- Physically bakes the rotation into the pixel array using hardware-accelerated CoreGraphics rendering.
- Outputs a perfectly upright image that renders correctly in any browser or viewer.
Dimension Constraints (Downscaling)
PixelTamp allows you to constrain image dimensions based on the longest edge:
- Original Size: Keeps native pixel dimensions untouched.
- 2560px (Default): Ideal for high-density Retina display hero banners.
- 1920px: Standard Full HD resolution for blog articles and content cards.
- 1024px: Compact size for thumbnails, avatars, and email newsletters.
PixelTamp operates strictly non-destructively: it will never upscale an image that is already smaller than the selected constraint.
Scope & Responsive Images
PixelTamp is built specifically for 1:1 asset optimisation. It is designed to compress source media or batches of pre-sized responsive images exported from your design tools.
It is not a bulk variant generator for creating multiple srcset resolutions from a single master file. The app stays deliberately focused on doing one thing exceptionally well: taking a given image or video and eliminating every unnecessary byte without visible quality loss.