JPGからPNGへの変換ツール

Joint Photographic Experts Group JFIF format

Note, JPG is a lossy compression. In addition, you cannot create black and white images with JPG nor can you save transparency. Requires jpegsrc.v8c.tar.gz. You can set quality scaling for luminance and chrominance separately (e.g. -quality 90,70). You can optionally define the DCT method, for example to specify the float method, use -define jpeg:dct-method=float. By default we compute optimal Huffman coding tables. Specify -define jpeg:optimize-coding=false to use the default Huffman tables. Two other options include -define jpeg:block-smoothing and -define jpeg:fancy-upsampling. Set the sampling factor with -define jpeg:sampling-factor. You can size the image with jpeg:size, for example -define jpeg:size=128x128. To restrict the maximum file size, use jpeg:extent, for example -define jpeg:extent=400KB. To define one or more custom quantization tables, use -define jpeg:q-table=filename. These values are multiplied by -quality argument divided by 100.0. To avoid reading a particular associated image profile, use -define profile:skip=name (e.g. profile:skip=ICC).

Portable Network Graphics

Requires libpng-1.0.11 or later, libpng-1.2.5 or later recommended. The PNG specification does not support pixels-per-inch units, only pixels-per-centimeter. To avoid reading a particular associated image profile, use -define profile:skip=name (e.g. profile:skip=ICC).