cygwin - Tesseract 运行时错误 : Error in pixReadMemPng: function not present

Question

我在 Cygwin 上构建了 Tesseract 3.04.01。它可以识别 .bmp 文件，但无法识别 .png 文件:

$ tesseract.exe 测试/phototest.png 输出
Tesseract Open Source OCR Engine v3.04.01 with Leptonica
pixReadMemPng 中的错误:函数不存在
pixReadMem 中的错误:png:没有返回 pix
处理过程中出错。

我以为leptopnica增加了对png的支持？

Answer 1

经过更多的挖掘，结果证明leptonica更像是libpng和libtiff等标准库的包装器，它会静默禁用支持 对于图像类型，如果无法找到它的库。

运行时它给了我这个 ./configure :

checking for png_read_png in -lpng... no

So I had to download and build libpng. After that it still didn't work, because libpng installed in /usr/local/lib, and apparently that is not a default library path for cygwin. So I had to use add it using LDFLAGS:

LDFLAGS=-L/usr/local/lib ./configure

之后，它最终构建了 PNG 支持，并给出了以下消息:

checking for png_read_png in -lpng... yes

出于某种原因，Makefile 中的链接顺序混淆了 - -lpng -lz ，这导致链接 liblept.la 失败:

png.c:(.text+0x13ab): undefined reference to `crc32'

我能解决的唯一方法是运行 make V=1 (详细模式)查看实际命令，即:

make[2]: Entering directory '/home/sasho/leptonica-1.73/src'
/bin/sh ../libtool  --tag=CC   --mode=link gcc  -g -O2 -no-undefined -version-info 5:0:0 -Wl,--as-needed -L/usr/local/lib -o liblept.la -rpath /usr/local/lib adaptmap.lo affine.lo affinecompose.lo arrayaccess.lo bardecode.lo baseline.lo bbuffer.lo bilateral.lo bilinear.lo binarize.lo binexpand.lo binreduce.lo blend.lo bmf.lo bmpio.lo bmpiostub.lo bootnumgen1.lo bootnumgen2.lo boxbasic.lo boxfunc1.lo boxfunc2.lo boxfunc3.lo boxfunc4.lo bytearray.lo ccbord.lo ccthin.lo classapp.lo colorcontent.lo coloring.lo colormap.lo colormorph.lo colorquant1.lo colorquant2.lo colorseg.lo colorspace.lo compare.lo conncomp.lo convertfiles.lo convolve.lo correlscore.lo dewarp1.lo dewarp2.lo dewarp3.lo dewarp4.lo dnabasic.lo dwacomb.2.lo dwacomblow.2.lo edge.lo encoding.lo enhance.lo fhmtauto.lo fhmtgen.1.lo fhmtgenlow.1.lo finditalic.lo flipdetect.lo fliphmtgen.lo fmorphauto.lo fmorphgen.1.lo fmorphgenlow.1.lo fpix1.lo fpix2.lo gifio.lo gifiostub.lo gplot.lo graphics.lo graymorph.lo grayquant.lo grayquantlow.lo heap.lo jbclass.lo jp2kheader.lo jp2kheaderstub.lo jp2kio.lo jp2kiostub.lo jpegio.lo jpegiostub.lo kernel.lo leptwin.lo libversions.lo list.lo map.lo maze.lo morph.lo morphapp.lo morphdwa.lo morphseq.lo numabasic.lo numafunc1.lo numafunc2.lo pageseg.lo paintcmap.lo parseprotos.lo partition.lo pdfio1.lo pdfio1stub.lo pdfio2.lo pdfio2stub.lo pix1.lo pix2.lo pix3.lo pix4.lo pix5.lo pixabasic.lo pixacc.lo pixafunc1.lo pixafunc2.lo pixalloc.lo pixarith.lo pixcomp.lo pixconv.lo pixlabel.lo pixtiling.lo pngio.lo pngiostub.lo pnmio.lo pnmiostub.lo projective.lo psio1.lo psio1stub.lo psio2.lo psio2stub.lo ptabasic.lo ptafunc1.lo ptra.lo quadtree.lo queue.lo rank.lo rbtree.lo readbarcode.lo readfile.lo recogbasic.lo recogdid.lo recogident.lo recogtrain.lo regutils.lo rop.lo ropiplow.lo roplow.lo rotate.lo rotateam.lo rotateamlow.lo rotateorth.lo rotateshear.lo runlength.lo sarray.lo scale.lo scalelow.lo seedfill.lo seedfilllow.lo sel1.lo sel2.lo selgen.lo shear.lo skew.lo spixio.lo stack.lo stringcode.lo sudoku.lo textops.lo tiffio.lo tiffiostub.lo utils.lo viewfiles.lo warper.lo watershed.lo webpio.lo webpiostub.lo writefile.lo zlibmem.lo zlibmemstub.lo  -lz -lpng       

然后我执行了相同的命令(来自 ./src 作为当前目录，否则它将不起作用)，但我附加了另一个 -lz最后，这使它成功。之后我只是重新运行 make，它继续构建库的其余部分。

cd src
/bin/sh ../libtool  --tag=CC   --mode=link gcc  -g -O2 -no-undefined -version-info 5:0:0 -Wl,--as-needed -L/usr/local/lib -o liblept.la -rpath /usr/local/lib adaptmap.lo affine.lo affinecompose.lo arrayaccess.lo bardecode.lo baseline.lo bbuffer.lo bilateral.lo bilinear.lo binarize.lo binexpand.lo binreduce.lo blend.lo bmf.lo bmpio.lo bmpiostub.lo bootnumgen1.lo bootnumgen2.lo boxbasic.lo boxfunc1.lo boxfunc2.lo boxfunc3.lo boxfunc4.lo bytearray.lo ccbord.lo ccthin.lo classapp.lo colorcontent.lo coloring.lo colormap.lo colormorph.lo colorquant1.lo colorquant2.lo colorseg.lo colorspace.lo compare.lo conncomp.lo convertfiles.lo convolve.lo correlscore.lo dewarp1.lo dewarp2.lo dewarp3.lo dewarp4.lo dnabasic.lo dwacomb.2.lo dwacomblow.2.lo edge.lo encoding.lo enhance.lo fhmtauto.lo fhmtgen.1.lo fhmtgenlow.1.lo finditalic.lo flipdetect.lo fliphmtgen.lo fmorphauto.lo fmorphgen.1.lo fmorphgenlow.1.lo fpix1.lo fpix2.lo gifio.lo gifiostub.lo gplot.lo graphics.lo graymorph.lo grayquant.lo grayquantlow.lo heap.lo jbclass.lo jp2kheader.lo jp2kheaderstub.lo jp2kio.lo jp2kiostub.lo jpegio.lo jpegiostub.lo kernel.lo leptwin.lo libversions.lo list.lo map.lo maze.lo morph.lo morphapp.lo morphdwa.lo morphseq.lo numabasic.lo numafunc1.lo numafunc2.lo pageseg.lo paintcmap.lo parseprotos.lo partition.lo pdfio1.lo pdfio1stub.lo pdfio2.lo pdfio2stub.lo pix1.lo pix2.lo pix3.lo pix4.lo pix5.lo pixabasic.lo pixacc.lo pixafunc1.lo pixafunc2.lo pixalloc.lo pixarith.lo pixcomp.lo pixconv.lo pixlabel.lo pixtiling.lo pngio.lo pngiostub.lo pnmio.lo pnmiostub.lo projective.lo psio1.lo psio1stub.lo psio2.lo psio2stub.lo ptabasic.lo ptafunc1.lo ptra.lo quadtree.lo queue.lo rank.lo rbtree.lo readbarcode.lo readfile.lo recogbasic.lo recogdid.lo recogident.lo recogtrain.lo regutils.lo rop.lo ropiplow.lo roplow.lo rotate.lo rotateam.lo rotateamlow.lo rotateorth.lo rotateshear.lo runlength.lo sarray.lo scale.lo scalelow.lo seedfill.lo seedfilllow.lo sel1.lo sel2.lo selgen.lo shear.lo skew.lo spixio.lo stack.lo stringcode.lo sudoku.lo textops.lo tiffio.lo tiffiostub.lo utils.lo viewfiles.lo warper.lo watershed.lo webpio.lo webpiostub.lo writefile.lo zlibmem.lo zlibmemstub.lo  -lz -lpng -lz      
cd -
make