PNG から JPG へのオンライン変換

PNG ファイルを JPG 形式に3ステップで簡単変換。

JPG⌄

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⚙ オプション設定

Resize

Color Filter

DPI

dpi

Crop (px)

PNG vs JPG：完全なフォーマットガイド

PNG

Lossless

圧縮

JPG

Lossy

PNG

Full 8-bit alpha channel — each pixel can be any opacity level from fully transparent (0) to fully opaque (255)

透明度

JPG

Not supported — transparent areas always render as solid white or the specified matte color

PNG

Not in standard PNG; APNG (Animated PNG) is a non-standard extension with limited, inconsistent support

アニメーション

JPG

Not supported

PNG

24-bit RGB (16.7M colors) or 32-bit RGBA (16.7M colors + full alpha); up to 48-bit for professional workflows

色深度

JPG

24-bit (8 bits per channel: RGB) — up to 16.7 million colors

PNG

100 KB – 10 MB — significantly larger than JPG for photographic content

ファイルサイズ

JPG

50 KB – 5 MB per image depending on resolution and quality setting

PNG

Universal — all modern browsers, operating systems, and devices including IE7+

ブラウザサポート

JPG

Universal — all browsers, all operating systems, all devices including IE6 and older smartphones

PNG

Graphics, logos, UI

最適な用途

JPG

Photos, web images

一般的なユースケース：PNG → JPG

📸 Web photography publishing📧 Email photo attachments📱 Social media image posts🖨️ Online photo printing🛒 Product photography catalogs📰 Blog and editorial images

⚠️Transparent areas in the source PNG will become solid white in the converted JPG output. Only convert PNG images without transparency. For transparent graphics intended for web use, WebP is a far better target format.

Format

PNG

PNG was created in 1996 as a free, patent-unencumbered alternative to GIF after Unisys enforced its LZW compression patent. The PNG Development Group introduced full-color support, genuine alpha trans…

長所

+Lossless — every pixel preserved with zero compression artifacts

+Full 8-bit alpha channel for smooth, semi-transparent edges

+Ideal for text, logos, and graphics where sharpness is non-negotiable

+Unlimited re-saves without any quality degradation whatsoever

制限事項

−3–5× larger than JPG for photographic content

−No native animation support in standard PNG

−Slower to load than WebP for equivalent image content

−Not practical for very high-resolution photographs at web scale

Logos, icons, and brand marks placed over any background colorScreenshots where text must remain perfectly sharpImages edited in multiple passes (keep as the master file)Web UI elements, buttons, icons, and interface assets

Format

JPG

Standardized in 1992 by the Joint Photographic Experts Group, JPEG became the internet's dominant image format through the 1990s. Its DCT compression made digital photography practical for early web a…

長所

+Smallest file sizes for photographs (10:1 to 20:1 compression ratio)

+Universal compatibility across every device, software, and platform

+Embeds EXIF metadata (GPS, camera settings, date/time)

+Adjustable quality/size trade-off at save time

制限事項

−Lossy — permanently discards image data with every save

−No transparency — backgrounds are always solid

−Visible block artifacts on sharp edges, text, and high-contrast areas

−Quality degrades with each re-save (generational quality loss)

Sharing photographs on social media, email, or blogsCamera images where file size matters more than pixel perfectionWeb page photos where page load speed is the priorityAny context requiring maximum cross-device and software compatibility

PNG から JPG：知っておくべきこと

PNGはグラフィックスに最適な可逆形式ですが、WebサイトやアプリケーションをSlows させる大きなファイルを生成します。PNGをJPGに変換すると、写真コンテンツでの知覚可能な品質損失を最小限に抑えながら、ファイルサイズを60〜80%削減するインテリジェントな圧縮が適用されます。

なぜ PNG を JPG に変換するのか？

⚡

より速いWebサイト

JPGファイルは写真の場合PNGより大幅に速く読み込まれ、サイトのパフォーマンスを向上させます。

ストレージ効率

5MBのPNG写真がJPGとして500KBに圧縮され、90%のストレージスペースを節約できます。

💾

📷

写真標準

一眼レフカメラ、ストックフォトサイト、写真サービスはすべてJPGをプライマリ配信形式として使用しています。

印刷互換性

フォトラボとプリントオンデマンドサービスはすべての印刷ジョブにJPGを普遍的に受け入れています。

🖨️

PNG

ファイル拡張子.png
説明PNG (Portable Network Graphics) is a lossless raster image format that supports transparency. Ideal for graphics, logos, icons, and images that require a transparent background.
関連プログラムAdobe Photoshop, GIMP, Microsoft Paint, Preview (Mac)
開発者PNG Development Group
MIME タイプimage/png

JPG

ファイル拡張子.jpg
説明JPEG (Joint Photographic Experts Group) is the most widely used lossy image compression format, ideal for photographs and complex images with many colors. JPEG achieves small file sizes by discarding some image data, making it perfect for web use and sharing.
関連プログラムAdobe Photoshop, GIMP, Windows Photo Viewer, Preview (Mac)
開発者Joint Photographic Experts Group
MIME タイプimage/jpeg