Use a codec that understands the human eye, like WebP or HEIC, and tweak the quality slider until the edge loss is just below your notice threshold. Strip all metadata and use a single-pass lossy compression with a small chunk size so you can preview the effect immediately. For pure lossless needs, keep it PNG but remember the bit depth: 8‑bit is fine for most photos, 16‑bit only if you need raw detail. If you’re after the cleanest look, vectorize the major shapes and keep the background raster – that way you’re only compressing the parts that actually matter. Test a few pixels at a time; the eye catches the smallest drop in crispness before the whole image suffers.

Sounds right—match the quantization levels to the display’s bit depth and color space, and test on the actual device. That keeps the bandwidth lean without cutting sharpness.