go語言中pdf轉圖片功能的實現(CentOS)
一、centos下環境部署
步驟1：部署ImageMagick
(2)解壓剛才下載的檔案： tar xvf ImageMagick-6.9.9-36.tar.gz
(3)進入解壓目錄：cd ImageMagick-6.9.9-36
(4)檢查配置：./configure
(5)安裝jpeg：yum install libjpeg* libpng* freetype* gd*
(6)安裝ImageMagick：make install
輸入convert -resize 100x100 hua.jpg hua1.jpg 如果執行成功，表明安裝成功。我在安裝的時候報錯如下：
{[Error:Command failed:convert:nodecode delegate for this image format `JPEG' @ error/constitute.c/ReadImage/501.
convert: no images defined `/home/node/head/I/IMG_0005.JPG' @ error/convert.c/ConvertImageCommand/3230.
] code: 1, signal: null }
解決辦法：重灌Imagemagick
make uninstall
./configure
make
make install
再次呼叫成功。
(7)環境變數配置： 進入/etc/profile,寫入
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig/
export MAGICK_CODER_MODULE_PATH=/data/download/ImageMagick-6.9.9-36/coders/
其中MAGICK_CODER_MODULE_PATH指ImageMagick-6.9.9-36安裝目錄下的coders(需要將/usr/local/lib下面的.so複製到該路徑下),PKG_CONFIG_PATH路徑下的內容如圖中所示：
步驟2：部署GhostScript
(1)下載安裝 GhostScript，官網地址：http://ghostscript.com/download/gsdnld.html。我這裡下載的是ghostscript-9.22-linux-x86_64.tgz
(2)解壓剛才下載的檔案： tar xvf ghostscript-9.22-linux-x86_64.tgz
(3)進入解壓目錄，將gs直接複製到 /usr/bin 目錄下
(4)進入/usr/bin 目錄中，chmod 777 gs
(5)輸入命令 gs -version 如果有如下輸出，說明安裝成功，列印的是版本：
二、程式碼實現
步驟2：go實現程式碼如下
package main
import (
"os"
"strconv"
"gopkg.in/gographics/imagick.v2/imagick"
)
func main() {
ConvertPdfToImage("test.pdf", 800, 1212, 200, 85)
}
//ConvertPdfToImage 轉換pdf為圖片格式
//@resolution:掃描精度
//@CompressionQuality:圖片質量: 1~100
func ConvertPdfToImage(bookname string, pageWidth uint, pageHeight uint, resolution float64, compressionQuality uint) (err error) {
imagick.Initialize()
defer imagick.Terminate()
mw := imagick.NewMagickWand()
//defer mw.Clear()
defer mw.Destroy()
if err := mw.SetResolution(resolution, resolution); err != nil {
println("掃描精度設定失敗")
return err
}
if err := mw.ReadImage(bookname); err != nil {
println("檔案讀取失敗")
return err
}
var pages = int(mw.GetNumberImages())
println("頁數:", pages)
//裁剪會使頁數增加
addPages := 0
path := ""
for i := 0; i < pages; i++ {
mw.SetIteratorIndex(i) // This being the page offset
//壓平影象，去掉alpha通道，防止JPG中的alpha變黑,用在ReadImage之後
if err := mw.SetImageAlphaChannel(imagick.ALPHA_CHANNEL_FLATTEN); err != nil {
println("圖片")
return err
}
mw.SetImageFormat("jpg")
mw.SetImageCompression(imagick.COMPRESSION_JPEG)
mw.SetImageCompressionQuality(compressionQuality)
//如果width>height ,就裁剪成兩張
pWidth := mw.GetImageWidth()
pHeight := mw.GetImageHeight()
//需要裁剪
if pWidth > pHeight {
//mw.ResizeImage(pageWidth*2, pageHeight, imagick.FILTER_UNDEFINED, 1.0)
mw.ThumbnailImage(pageWidth*2, pageHeight)
tempImage := mw.GetImageFromMagickWand()
leftMw := imagick.NewMagickWandFromImage(tempImage) //由於返回的是指標,需要提前初始化,不然寫完左半業tempImage就變了
//左半頁
mw.CropImage(pageWidth, pageHeight, 0, 0)
path = "./book/page" + strconv.Itoa(i+addPages) + ".jpg"
mw.WriteImage(path)
//右半頁
leftMw.SetImageFormat("jpg")
leftMw.SetImageCompression(imagick.COMPRESSION_JPEG)
leftMw.SetImageCompressionQuality(compressionQuality)
leftMw.CropImage(pageWidth, pageHeight, int(pageWidth), 0)
addPages++
path = "./book/page" + strconv.Itoa(i+addPages) + ".jpg"
leftMw.WriteImage(path)
leftMw.Destroy()
} else {
mw.ThumbnailImage(pageWidth, pageHeight)
path = "./book/page" + strconv.Itoa(i+addPages) + ".jpg"
mw.WriteImage(path)
}
}
println("轉換完畢!")
os.Exit(0) //模擬退出程式,刪掉!
return nil
}三、問題解決
在執行過程中報錯如下：
問題一：../gopkg.in/gographics/imagick.v2/imagick/drawing_wand.go:39: undefined: runtime.KeepAlive
解決：go版本過低導致
問題二：go build gopkg.in/gographics/imagick.v2/imagick: invalid flag in pkg-config --cflags: -fopenmp
解決：go版本原因。
問題三：/tmp/go-build695941684/command-line-arguments/_obj/exe/pdfconvert: error while loading shared libraries: libMagickWand-6.Q16.so.5: cannot open shared object file: No such file or directory
解決：進入目錄/user/local/lib中，執行ldconfig /user/local/lib。即解決。
參考文章：http://blog.csdn.net/gaofuqi/article/details/26698547
http://blog.csdn.net/lisaem/article/details/50330953
http://blog.csdn.net/catoop/article/details/42677021
http://blog.csdn.net/arackethis/article/details/42241471