画像ガイド
リサイズ・切り抜き・変換の途中で出てくる疑問への、短く実用的な答え。
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Social media image sizes — a cheat sheet that actually saves you time
The pixel sizes that matter for Instagram, YouTube, X, LinkedIn, Facebook and Pinterest, plus the three rules that let you stop looking sizes up altogether.
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How to get an image under an upload limit — without it looking bad
A repeatable order of operations for shrinking image files: dimensions first, then format, then quality. With realistic numbers for a 2 MB form, a 25 MB email and a web page.
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WebP vs AVIF vs JPEG vs PNG — which format, and when
A practical comparison of the four image formats that matter in 2026: compression, browser and app support, transparency, and a decision list you can follow in ten seconds.
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How to resize an image without losing quality
What actually degrades an image when you resize it, why downscaling in steps looks better, why upscaling cannot work, and what DPI has to do with any of it.