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画像を引き伸ばさずにリサイズする方法

縦横比を崩さずに、写真やスクリーンショットを自然にリサイズする方法を解説します。

画像の伸びは、縦横比を無視して幅と高さを個別に変更すると起こります。比率固定を基本にすると失敗を防げます。

Understand what causes stretching

Every image has a native width-to-height ratio.

When you force both dimensions to unrelated numbers, the picture distorts.

Keep aspect ratio lock enabled by default

Set either width or height first and let the other value auto-adjust.

This preserves natural shape for people, products, UI screenshots, and logos.

Resize to real layout targets

Pick dimensions based on where the image will actually appear.

Matching layout width reduces guesswork and prevents unnecessary edits.

  • Check the image slot width in your page builder.
  • Use one standard width per placement type.
  • Export a second size only when layout truly differs.

Use crop only when composition needs it

Cropping can improve framing, but it should be intentional.

Do not use random cropping as a fix for stretched outputs.

Do a final visual check before upload

Preview at normal zoom on desktop and mobile.

If circles, faces, or text look natural, your resize settings are safe to reuse.

Use this when

  • Your resized images look squashed or widened.
  • Screenshot text becomes oddly stretched after editing.
  • You need clean visuals for blog or product pages.
  • You want a repeatable beginner-friendly resizing process.

Protect aspect ratio first

If you keep proportions locked and resize to real display width, most stretching problems disappear immediately.

関連ツール

画像リサイズ

目標サイズを指定して、WebやSNS向けのPNGまたはJPGを書き出せます。

Open Image Resizer

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