Dopo aver provato per oltre due ore, posso tranquillamente affermare che tutto il metodo menzionato finora non funziona su tutti i browser, o per IE anche tra le versioni del browser ...
Ad esempio (risposta più votata):
filter: progid:DXImageTransform.Microsoft.BasicImage(rotation=0.083); /* IE6,IE7 */
-ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=0.083)"; /* IE8 */
ruota due volte in IE9, una volta per filtro e una volta per -ms-filter, quindi ...
Anche tutti gli altri metodi menzionati non funzionano, almeno non se non devi impostare un'altezza / larghezza fissa della cella dell'intestazione della tabella (con colore di sfondo), dove dovrebbe adattarsi automaticamente alla dimensione dell'elemento più alto.
Quindi per approfondire la generazione di immagini lato server proposta da Nathan Long, che è davvero l'unico metodo universalmente funzionante, ecco il mio codice VB.NET per un gestore generico (* .ashx):
Imports System.Web
Imports System.Web.Services
Public Class GenerateImage
Implements System.Web.IHttpHandler
Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
'context.Response.ContentType = "text/plain"
'context.Response.Write("Hello World!")
context.Response.ContentType = "image/png"
Dim strText As String = context.Request.QueryString("text")
Dim strRotate As String = context.Request.QueryString("rotate")
Dim strBGcolor As String = context.Request.QueryString("bgcolor")
Dim bRotate As Boolean = True
If String.IsNullOrEmpty(strText) Then
strText = "No Text"
End If
Try
If Not String.IsNullOrEmpty(strRotate) Then
bRotate = System.Convert.ToBoolean(strRotate)
End If
Catch ex As Exception
End Try
'Dim img As System.Drawing.Image = GenerateImage(strText, "Arial", bRotate)
'Dim img As System.Drawing.Image = CreateBitmapImage(strText, bRotate)
' Generic error in GDI+
'img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png)
'Dim bm As System.Drawing.Bitmap = New System.Drawing.Bitmap(img)
'bm.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png)
Using msTempOutputStream As New System.IO.MemoryStream
'Dim img As System.Drawing.Image = GenerateImage(strText, "Arial", bRotate)
Using img As System.Drawing.Image = CreateBitmapImage(strText, bRotate, strBGcolor)
img.Save(msTempOutputStream, System.Drawing.Imaging.ImageFormat.Png)
msTempOutputStream.Flush()
context.Response.Buffer = True
context.Response.ContentType = "image/png"
context.Response.BinaryWrite(msTempOutputStream.ToArray())
End Using ' img
End Using ' msTempOutputStream
End Sub ' ProcessRequest
Private Function CreateBitmapImage(strImageText As String) As System.Drawing.Image
Return CreateBitmapImage(strImageText, True)
End Function ' CreateBitmapImage
Private Function CreateBitmapImage(strImageText As String, bRotate As Boolean) As System.Drawing.Image
Return CreateBitmapImage(strImageText, bRotate, Nothing)
End Function
Private Function InvertMeAColour(ColourToInvert As System.Drawing.Color) As System.Drawing.Color
Const RGBMAX As Integer = 255
Return System.Drawing.Color.FromArgb(RGBMAX - ColourToInvert.R, RGBMAX - ColourToInvert.G, RGBMAX - ColourToInvert.B)
End Function
Private Function CreateBitmapImage(strImageText As String, bRotate As Boolean, strBackgroundColor As String) As System.Drawing.Image
Dim bmpEndImage As System.Drawing.Bitmap = Nothing
If String.IsNullOrEmpty(strBackgroundColor) Then
strBackgroundColor = "#E0E0E0"
End If
Dim intWidth As Integer = 0
Dim intHeight As Integer = 0
Dim bgColor As System.Drawing.Color = System.Drawing.Color.LemonChiffon ' LightGray
bgColor = System.Drawing.ColorTranslator.FromHtml(strBackgroundColor)
Dim TextColor As System.Drawing.Color = System.Drawing.Color.Black
TextColor = InvertMeAColour(bgColor)
'TextColor = Color.FromArgb(102, 102, 102)
' Create the Font object for the image text drawing.
Using fntThisFont As New System.Drawing.Font("Arial", 11, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Pixel)
' Create a graphics object to measure the text's width and height.
Using bmpInitialImage As New System.Drawing.Bitmap(1, 1)
Using gStringMeasureGraphics As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(bmpInitialImage)
' This is where the bitmap size is determined.
intWidth = CInt(gStringMeasureGraphics.MeasureString(strImageText, fntThisFont).Width)
intHeight = CInt(gStringMeasureGraphics.MeasureString(strImageText, fntThisFont).Height)
' Create the bmpImage again with the correct size for the text and font.
bmpEndImage = New System.Drawing.Bitmap(bmpInitialImage, New System.Drawing.Size(intWidth, intHeight))
' Add the colors to the new bitmap.
Using gNewGraphics As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(bmpEndImage)
' Set Background color
'gNewGraphics.Clear(Color.White)
gNewGraphics.Clear(bgColor)
gNewGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias
gNewGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias
''''
'gNewGraphics.TranslateTransform(bmpEndImage.Width, bmpEndImage.Height)
'gNewGraphics.RotateTransform(180)
'gNewGraphics.RotateTransform(0)
'gNewGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SystemDefault
gNewGraphics.DrawString(strImageText, fntThisFont, New System.Drawing.SolidBrush(TextColor), 0, 0)
gNewGraphics.Flush()
If bRotate Then
'bmpEndImage = rotateImage(bmpEndImage, 90)
'bmpEndImage = RotateImage(bmpEndImage, New PointF(0, 0), 90)
'bmpEndImage.RotateFlip(RotateFlipType.Rotate90FlipNone)
bmpEndImage.RotateFlip(System.Drawing.RotateFlipType.Rotate270FlipNone)
End If ' bRotate
End Using ' gNewGraphics
End Using ' gStringMeasureGraphics
End Using ' bmpInitialImage
End Using ' fntThisFont
Return bmpEndImage
End Function ' CreateBitmapImage
' http://msdn.microsoft.com/en-us/library/3zxbwxch.aspx
' http://msdn.microsoft.com/en-us/library/7e1w5dhw.aspx
' http://www.informit.com/guides/content.aspx?g=dotnet&seqNum=286
' http://road-blogs.blogspot.com/2011/01/rotate-text-in-ssrs.html
Public Shared Function GenerateImage_CrappyOldReportingServiceVariant(ByVal strText As String, ByVal strFont As String, bRotate As Boolean) As System.Drawing.Image
Dim bgColor As System.Drawing.Color = System.Drawing.Color.LemonChiffon ' LightGray
bgColor = System.Drawing.ColorTranslator.FromHtml("#E0E0E0")
Dim TextColor As System.Drawing.Color = System.Drawing.Color.Black
'TextColor = System.Drawing.Color.FromArgb(255, 0, 0, 255)
If String.IsNullOrEmpty(strFont) Then
strFont = "Arial"
Else
If strFont.Trim().Equals(String.Empty) Then
strFont = "Arial"
End If
End If
'Dim fsFontStyle As System.Drawing.FontStyle = System.Drawing.FontStyle.Regular
Dim fsFontStyle As System.Drawing.FontStyle = System.Drawing.FontStyle.Bold
Dim fontFamily As New System.Drawing.FontFamily(strFont)
Dim iFontSize As Integer = 8 '//Change this as needed
' vice-versa, because 270° turn
'Dim height As Double = 2.25
Dim height As Double = 4
Dim width As Double = 1
' width = 10
' height = 10
Dim bmpImage As New System.Drawing.Bitmap(1, 1)
Dim iHeight As Integer = CInt(height * 0.393700787 * bmpImage.VerticalResolution) 'y DPI
Dim iWidth As Integer = CInt(width * 0.393700787 * bmpImage.HorizontalResolution) 'x DPI
bmpImage = New System.Drawing.Bitmap(bmpImage, New System.Drawing.Size(iWidth, iHeight))
'// Create the Font object for the image text drawing.
'Dim MyFont As New System.Drawing.Font("Arial", iFontSize, fsFontStyle, System.Drawing.GraphicsUnit.Point)
'// Create a graphics object to measure the text's width and height.
Dim MyGraphics As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(bmpImage)
MyGraphics.Clear(bgColor)
Dim stringFormat As New System.Drawing.StringFormat()
stringFormat.FormatFlags = System.Drawing.StringFormatFlags.DirectionVertical
'stringFormat.FormatFlags = System.Drawing.StringFormatFlags.DirectionVertical Or System.Drawing.StringFormatFlags.DirectionRightToLeft
Dim solidBrush As New System.Drawing.SolidBrush(TextColor)
Dim pointF As New System.Drawing.PointF(CSng(iWidth / 2 - iFontSize / 2 - 2), 5)
Dim font As New System.Drawing.Font(fontFamily, iFontSize, fsFontStyle, System.Drawing.GraphicsUnit.Point)
MyGraphics.TranslateTransform(bmpImage.Width, bmpImage.Height)
MyGraphics.RotateTransform(180)
MyGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SystemDefault
MyGraphics.DrawString(strText, font, solidBrush, pointF, stringFormat)
MyGraphics.ResetTransform()
MyGraphics.Flush()
'If Not bRotate Then
'bmpImage.RotateFlip(System.Drawing.RotateFlipType.Rotate90FlipNone)
'End If
Return bmpImage
End Function ' GenerateImage
ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
Get
Return False
End Get
End Property ' IsReusable
End Class
Nota che se pensi che questa parte
Using msTempOutputStream As New System.IO.MemoryStream
'Dim img As System.Drawing.Image = GenerateImage(strText, "Arial", bRotate)
Using img As System.Drawing.Image = CreateBitmapImage(strText, bRotate, strBGcolor)
img.Save(msTempOutputStream, System.Drawing.Imaging.ImageFormat.Png)
msTempOutputStream.Flush()
context.Response.Buffer = True
context.Response.ContentType = "image/png"
context.Response.BinaryWrite(msTempOutputStream.ToArray())
End Using ' img
End Using ' msTempOutputStream
può essere sostituito con
img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png)
poiché funziona sul server di sviluppo, ti sbagli di grosso nel presumere che lo stesso codice non genererebbe un'eccezione GDI + generica se lo distribuisci su un server Windows 2003 IIS 6 ...
quindi usalo in questo modo:
<img alt="bla" src="GenerateImage.ashx?no_cache=123&text=Hello%20World&rotate=true" />
