image - 提升图片上传、调整大小、存入数据库、显示

Question

是否有一个简洁的示例说明如何上传图像、调整大小、将其存储在数据库中，然后使用 Lift 提供图像？

我确信我可以将文件上传、Java 2D API、Lift Mapper 和响应 API 拼凑起来。但是有没有我可以遵循的示例代码以“正确”或推荐的方式进行操作？

Answer 1

我通过创建一个新的 MappedField 为链接到 s3 的 Mapper 字段执行此操作。我还有一些代码要调整大小，但尚未测试或部署（因此请谨慎使用）。

class MappedS3Image[T<:Mapper[T]](owner: T, val path:String, maxWidth: String, maxHeight:String) extends MappedString[T](owner, 36) {

  def url:String = MappedS3Image.fullImgPath(path, is)

  def setFromUpload(fileHolder: Box[FileParamHolder]) = {
      S3Sender.uploadImageToS3(path, fileHolder).map(this.set(_))
  }

  override def asHtml:Node = <img src={url} style={"max-width:" + maxWidth + ";max-height:"+maxHeight} />
  override def _toForm: Box[Elem] = Full(SHtml.fileUpload(fu=>setFromUpload(Full(fu))))

}


import java.awt.Image 
import java.awt.image.BufferedImage
import javax.imageio.ImageIO
import java.awt.Graphics2D
import java.awt.AlphaComposite

object ImageResizer {

    def resize(is:java.io.InputStream, maxWidth:Int, maxHeight:Int):BufferedImage = {
        val originalImage:BufferedImage = ImageIO.read(is)

        val height = originalImage.getHeight
        val width = originalImage.getWidth

        if (width <= maxWidth && height <= maxHeight)
            originalImage
        else {
            var scaledWidth:Int = width
            var scaledHeight:Int = height
            val ratio:Double = width/height
            if (scaledWidth > maxWidth){
                scaledWidth = maxWidth
                scaledHeight = (scaledWidth.doubleValue/ratio).intValue
            }
            if (scaledHeight > maxHeight){
                scaledHeight = maxHeight
                scaledWidth = (scaledHeight.doubleValue*ratio).intValue
            }
            val scaledBI = new BufferedImage(scaledWidth, scaledHeight,  BufferedImage.TYPE_INT_RGB)
            val g = scaledBI.createGraphics
            g.setComposite(AlphaComposite.Src)
            g.drawImage(originalImage, 0, 0, scaledWidth, scaledHeight, null);
            g.dispose
            scaledBI
        }
    }
}

Answer 2

另一个答案很好地描述了如何调整图像大小并将对文件的引用存储在文件系统上。

如果您想使用提升映射器来存储实际文件内容，您必须创建您的自定义模型对象，并在其上定义一个二进制字段。尝试这样的事情：

package code {
package model {


import _root_.net.liftweb.mapper._
import _root_.net.liftweb.util._
import _root_.net.liftweb.common._


// singleton object which manipulates storing of Document instances
object Document extends Document with KeyedMetaMapper[Long, Document] {
}



class Document extends KeyedMapper[Long, Document] {
  def getSingleton = Document
  def primaryKeyField = id

  object id extends MappedLongIndex(this)

  object name extends MappedString(this, 20) {
    override def displayName = "Name"
    override def writePermission_? = true
  }

  object content extends MappedBinary(this) {
    override def displayName = "Content"
    override def writePermission_? = true
  }
}



}
}

然后，在引导类中，Document在末尾添加：

Schemifier.schemify(true, Schemifier.infoF _, User, Document)

瞧。使用Document save (new Document)将其存储到数据库中。new Document可以使用该set方法设置A的字段。尝试使用单例的delete_!, find,findAll方法Document来删​​除或在数据库中找到它。从这一点开始应该是直截了当的。

最后，为了显示图像，您可以覆盖 Lift 的调度规则（在引导类中，Boot.scala）。尝试使用这个覆盖 pdf 请求规则的示例：

def getFile(filename: String): Option[Document] = {
  val alldocs = Document.findAll()
  alldocs.find(_.name.get == filename)
}

LiftRules.statelessDispatchTable.append {
  case Req("file" :: name :: Nil, "pdf", GetRequest) =>
    () =>
    println("Got request for: " + name + ".pdf")
    for {
      stream <- tryo(
        getFile(name + ".pdf") map { 
          doc => new java.io.ByteArrayInputStream(doc.content.get)
        } getOrElse null
      )
      if null ne stream
    } yield StreamingResponse(stream,
                              () => stream.close,
                              stream.available,
                              List("Content-Type" -> "application/pdf"),
                              Nil,
                              200)
}

Answer 3

根据 Jon Hoffman 接受的答案，我修复了这些错误。他的版本弄乱了纵横比（它总是变成 1:1），因为数学在一些地方是错误的。这个版本调整大图片的大小，直到它们适合，并尊重纵横比。

def resize(is:java.io.InputStream, maxWidth:Int, maxHeight:Int):BufferedImage = {
    require (maxWidth > 0)
    require (maxHeight > 0)
    val originalImage:BufferedImage = ImageIO.read(is)

    var height = originalImage.getHeight
    var width = originalImage.getWidth

    // Shortcut to save a pointless reprocessing in case the image is small enough already
    if (width <= maxWidth && height <= maxHeight)
        originalImage
    else {          
        // If the picture was too big, it will either fit by width or height.
        // This essentially resizes the dimensions twice, until it fits
        if (width > maxWidth){
          height = (height.doubleValue() * (maxWidth.doubleValue() / width.doubleValue())).intValue
          width = maxWidth
        }
        if (height > maxHeight){
          width = (width.doubleValue() * (maxHeight.doubleValue() / height.doubleValue())).intValue
          height = maxHeight
        }
        val scaledBI = new BufferedImage(width, height,  BufferedImage.TYPE_INT_RGB)
        val g = scaledBI.createGraphics
        g.setComposite(AlphaComposite.Src)
        g.drawImage(originalImage, 0, 0, width, height, null);
        g.dispose
        scaledBI
    }
}