有没有一个简洁的示例可以展示如何上传图像,调整其大小,将其存储在数据库中,然后使用Lift提供该图像?
我相信我可以从文件上传、Java 2D API、Lift Mapper和Response APIs中拼凑出来。但是是否有任何示例代码可以遵循以“正确”或推荐的方式执行操作?
有没有一个简洁的示例可以展示如何上传图像,调整其大小,将其存储在数据库中,然后使用Lift提供该图像?
我相信我可以从文件上传、Java 2D API、Lift Mapper和Response APIs中拼凑出来。但是是否有任何示例代码可以遵循以“正确”或推荐的方式执行操作?
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
}
}
}
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
}
}
}
}
Document
:Schemifier.schemify(true, Schemifier.infoF _, User, Document)
使用Document save (new Document)
将其存储到数据库中。可以使用set
方法设置new Document
的字段。尝试使用Document
单例的delete_!
、find
、findAll
方法删除或在数据库中查找它,从此处开始应该很简单。
最后,要显示图像,您可以覆盖Lift的调度规则(在引导类Boot.scala中)。尝试使用此示例,覆盖pdf请求的规则:
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)
}
基于Jon Hoffman所提供的答案,我修复了一些错误。他的版本会破坏图片的宽高比(它总是变成1:1),因为在一些地方数学计算有误。这个版本可以调整大图片的尺寸,直到它们适合,并保持它们的宽高比。
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
}
}