Question

我正在尝试将pdf文件的第一页转换为缩略图JPEG文件。我有类似于以下python代码的代码。

from tempfile import TemporaryFile, NamedTemporaryFile
import os
from subprocess import call
…
def createThumbnail(reporttempfile, thumbnailtempfile):
    # build the command for executing for extracting thumbnail
    command = "convert -resize 241x344 -background white -gravity center -extent 241x344 -quality 75" 
    csplit = command.split(' ')
    csplit.append("pdf:"+reporttempfile.name + "[0]")
    csplit.append(thumbnailtempfile.name)
    print "csplit = ", csplit
    print "cmd = %s" % " ".join(csplit)
    # run the command convert to create thumbnail
    retval = call(csplit)
    print "retval = %d" % retval
    return retval

当我调用上面的函数时，我得到以下输出：

csplit =  ['convert', '-resize', '241x344', '-background', 'white', '-gravity', 'center', '-extent', '241x344', '-quality', '75', 'pdf:/tmp/reportfile0001_zeEJ8B.pdf[0]', '/tmp/thumbnail0001_DTPHGb.jpg']

cmd = convert -resize 241x344 -background white -gravity center -extent 241x344 -quality 75 pdf:/tmp/reportfile0001_zeEJ8B.pdf[0] /tmp/thumbnail0001_DTPHGb.jpg
   **** Error: Cannot find a 'startxref' anywhere in the file.
   **** Warning:  An error occurred while reading an XREF table.
   **** The file has been damaged.  This may have been caused
   **** by a problem while converting or transfering the file.
   **** Ghostscript will attempt to recover the data.
   **** Error:  Trailer is not found.

Requested FirstPage is greater than the number of pages in the file: 0
   No pages will be processed (FirstPage > LastPage).

   **** This file had errors that were repaired or ignored.
   **** Please notify the author of the software that produced this
   **** file that it does not conform to Adobe's published PDF
   **** specification.

convert.im6: Postscript delegate failed `/tmp/reportfile0001_zeEJ8B.pdf': No such file or directory @ error/pdf.c/ReadPDFImage/677.
convert.im6: no images defined `/tmp/thumbnail0001_DTPHGb.jpg' @ error/convert.c/ConvertImageCommand/3044.
retval = 1
1

但是，当我通过在shell上键入来直接调用命令时，转换成功没有任何问题，我可以看到.jpg文件被正确转换。使用的命令是（也在上面的输出中打印）：

convert -resize 241x344 -background white -gravity center -extent 241x344 -quality 75 pdf:/tmp/reportfile0001_zeEJ8B.pdf[0] /tmp/thumbnail0001_DTPHGb.jpg

我在Mac上看到过这种行为（10.9.5），ImageMagick 6.9.0-0 Q16 x86_64 2015-04-09以及Ubuntu 14和ImageMagick 6.7.7-10 2014-03-06 Q16。

我知道为什么会发生这种情况。有人可以帮忙吗？

此致

SN

只有在通过python的subprocess.call调用时，ImageMagick的转换才会失败

0 个答案: