JPG に PNGコンバーター — 高速＆無料

Converting a JPG (JPEG) image to PNG format changes the file from a lossy-compressed raster image to a lossless-compressed one. JPEG uses Discrete Cosine Transform compression, which permanently discards fine detail to reduce file size — ideal for photographs but unsuitable when pixel-perfect fidelity is required. PNG uses DEFLATE lossless compression, meaning every pixel is preserved exactly as encoded. This makes PNG the preferred format for screenshots, diagrams, logos, and any image that contains sharp lines or flat areas of colour. The PNG output from a JPG-to-PNG conversion will be pixel-identical to the source JPEG, but the file size will typically be larger because lossless encoding retains all pixel data and no further compression artefacts are introduced. 1converter performs this conversion using ImageMagick, preserving ICC colour profiles, transparency channels (if applicable), and metadata such as EXIF orientation tags.