Image Compressor
Compress photographs and graphics in your browser, shrink file size while controlling quality, speed up uploads and conserve bandwidth for sharing or storage.Compression Result
| Size (KB) | Dimensions | |
|---|---|---|
| Original | {{ originalSizeKB }} | {{ originalWidth }} × {{ originalHeight }} |
| Compressed | {{ compressedSizeKB }} | {{ compressedWidth }} × {{ compressedHeight }} |
Introduction:
Digital image compression reduces the byte-count needed to represent photographs or graphics while maintaining acceptable visual fidelity. By eliminating perceptually redundant data or encoding pixels more efficiently, compressed files travel faster across networks, load sooner on webpages, and occupy less space on phones, servers, and backups.
This browser-side tool accepts a source picture, desired quality percentage, output format, and optional dimension limits. A client-side compression routine decodes the bitmap, applies chroma subsampling and quantisation scaled to the quality slider, then re-encodes the pixels as JPEG, PNG, or WebP—no data leaves the page at any point.
Imagine trimming a 5 MB holiday snapshot to 1.5 MB before emailing relatives; the message sends quicker and receivers download on limited mobile data, yet the scene remains recognisable. *Over-compressing intricate imagery can introduce block artefacts, so always keep a high-quality original as a safety copy.*
Technical Details:
Still-image compression exploits luminance sensitivity, spatial redundancy, and entropy coding to lower file size. Quality control modulates quantisation tables; optional resizing drops pixel-domain information; container choice (JPEG, PNG, WebP) determines entropy coder and colour subsampling. The balance among these variables shapes final fidelity and weight.
- Decode the original file into an uncompressed RGB pixel matrix (n × m × 3).
- Normalize orientation and strip or preserve metadata per user selection.
- Downscale to maxWidth or maxHeight if provided, maintaining aspect ratio.
- Convert colour to Y′CbCr, subsample chroma channels, then apply quality-weighted quantisation.
- Entropy-encode coefficients and package the stream as the chosen container format.
| Quality Band | Visual Impact |
|---|---|
| 90 – 100 % | Indistinguishable from source |
| 70 – 89 % | Balanced fidelity vs size |
| 50 – 69 % | Minor softness, good savings |
| 30 – 49 % | Noticeable artefacts on edges |
| 10 – 29 % | Strong blockiness and colour loss |
Choose a higher band when fine texture matters; select a lower band for thumbnails or quick previews.
- quality – integer 10-100 controlling quantisation strength.
- format – output container: JPEG, PNG, or WebP.
- retainExif – keep camera metadata when enabled.
- checkOrientation – auto-rotate using orientation flag.
- convertSizeKB – threshold for PNG-to-JPEG conversion.
- maxWidth / maxHeight – pixel ceiling for scaling.
Example: 4000 × 3000 px JPEG at 5 MB, quality 70 %, no resize.
Final file ≈ 1.5 MB; saving ≈ 68 %.
- Assumes sRGB colour space.
- Ignores alpha when exporting JPEG.
- Lossy modes permanently discard data.
- Quality 100 % still re-encodes; bit-identical output is not guaranteed.
- Very small icons may grow when forced into PNG.
- Photos with heavy grain exaggerate artefacts at low quality.
- Images using non-standard ICC profiles may shift colour.
- Metadata removal may strip geotags relied on by photo managers.
Compression strategies derive from widely studied discrete cosine transform theory and entropy coding fundamentals articulated by Wallace (1992) and Skodras et al. (2001).
No personal data leaves your device; processing occurs entirely within the browser sandbox.
Step-by-Step Guide:
Follow this sequence to generate a downsized file.
- Select an image from your device or drop it into the page.
- Move the quality slider until the percentage meets your goal.
- Pick the output format; WebP often yields the smallest size.
- Open “Advanced” to set maxWidth, maxHeight, or metadata options.
- Wait for the instant preview, then download the compressed copy.
FAQ:
Why does quality matter?
Lower quality increases quantisation, reducing file size but introducing blurring or blocking. Moderate values around 70 % balance detail and savings for most photos.
Which formats are supported?
The engine can produce JPEG, PNG, or WebP. JPEG suits photos, PNG retains transparency, and WebP offers modern compression across most browsers.
Does it keep metadata?
Set “Preserve EXIF metadata” to retain camera settings and geotags. Disabling it removes personal data and saves additional space.
Is my data stored?
No file is uploaded or recorded; all operations run locally in memory. Closing or refreshing the page clears every reference.
How is orientation handled?
When “Auto-rotate” is active, the tool reads the orientation flag and re-renders pixels upright before compression, preventing sideways previews.
Glossary:
- Quality Factor
- Numeric value shaping quantisation strength.
- Chroma Subsampling
- Allocation of fewer bytes to colour detail than luminance.
- Quantisation
- Rounding frequency coefficients to reduce precision.
- EXIF
- Metadata block storing camera, lens, and location data.
- Lossy Compression
- Technique that removes information unrecoverably.