PDF到JPEG转换器

Portable Document Format

Requires Ghostscript to read. By default, ImageMagick sets the page size to the MediaBox. Some PDF files, however, have a CropBox or TrimBox that is smaller than the MediaBox and may include white space, registration or cutting marks outside the CropBox or TrimBox. To force ImageMagick to use the CropBox or TrimBox rather than the MediaBox, use -define (e.g. -define pdf:use-cropbox=trueor -define pdf:use-trimbox=true). Use -density to improve the appearance of your PDF rendering (e.g. -density 300x300). Use -alpha remove to remove transparency. To specify direct conversion from Postscript to PDF, use -define delegate:bimodel=true. Use -define pdf:fit-page=true to scale to the page size. To immediately stop processing upon an error, set -define pdf:stop-on-error to true. To set the page direction preferences to right-to-left, try -define pdf:page-direction=right-to-left. Use -alpha remove to remove transparency. When writing to a PDF, thumbnails are included by default. To skip generating thumbnails, -define pdf:thumbnail=false. To enable interpolation when rendering, use -define pdf:interpolate=true.

Joint Photographic Experts Group JFIF format

Note, JPEG is a lossy compression. In addition, you cannot create black and white images with JPEG 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).