A sound implementation does not ask users to refresh until it works. Each phase has an input, an output, a timeout, and a terminal state. Screenshots and photos exceed display needs, but re-encoding loses quality, changes color, and costs CPU. Keep a send-original option and estimate size first.
Performance work starts with the full interval users wait, then separates CPU, queues, network, and persistence. Compare p95 and p99 with resource cost because averages hide the users most likely to leave.
Define the system contract first
Write the following choices as reviewable rules instead of scattering them across callbacks and UI conditions. Explicit rules make scaling, compatibility, and diagnosis less dependent on guesswork.
- Respect orientation, cap longest-edge pixels, use WebP/JPEG for photos and alpha-capable formats for transparency, process in a worker, and strip GPS EXIF by default.
- Give state one owner, a version, and terminal states; callbacks may mutate only the version that created them.
- Treat cleanup as protocol behavior: timers, handles, queues, and temporary data must be safely releasable in every terminal state.
The delivery standard for Compressing Images Before Transfer Without Losing Control of Quality is a usable normal path, convergent failures, bounded resources, and a state users can understand. The result is a production capability that can be explained, degraded safely, and rolled back—not a demo that works once.
What can break that contract
Boundaries turn hidden assumptions into incidents. Weak networks, refresh, concurrency, and capacity need combined coverage because retries can hide each one in isolation.
- Always converting to JPEG ruins transparent screenshots and text, while drawing a huge bitmap can allocate hundreds of MB and crash mobile.
- A boolean failure cannot distinguish retryable, user-action, and permanent refusal, producing an endless loop.
- An untested fallback receives all traffic during a primary failure and becomes the slower, more expensive bottleneck.
How to test the contract line by line
Build golden cases from known inputs and controlled faults, then align production metrics with those results. Verification extends to production only when signals detect the same degradation early.
- Test photos, transparent PNGs, tall screenshots, wide-gamut images, and GPS/orientation EXIF; compare size, quality proxy, peak memory, time, and metadata.
- Run one hundred start, fail, retry, and cancel cycles; handles, listeners, queues, and temporary data must return to baseline.
- Cover direct, relayed, weak-network, background-tab, and mobile paths; do not rely on averages or one successful screenshot.
Completion is not one passing path. Every terminal state reconciles, automation stays below user intent, and every operational cost has an explicit ceiling.