So here's my issue. I have an image that I need to shrink. The original image is a grayscale PNG, which isn't a huge issues except that when I shrink it down, the thermal label printers pickup the artifacts and print them on the label. So, what I did was change the image to black & white (Format1bppIndexed) before resizing, like this:
Dim bte() As Byte = System.Convert.FromBase64String(开发者_开发知识库imgStr)
Dim ms As New IO.MemoryStream(bte)
Dim bmp As New System.Drawing.Bitmap(ms)
Dim monoImage As Drawing.Bitmap = New Drawing.Bitmap(1200, 1800, Drawing.Imaging.PixelFormat.Format1bppIndexed)
Dim rect As New Drawing.Rectangle(0, 0, 1200, 1800)
monoImage = bmp.Clone(rect, Drawing.Imaging.PixelFormat.Format1bppIndexed)
And then I resize it. This code works fine on my Windows 7 machine, but when I run it on the Windows 2003 Server box that it calls home, it always throws an OutOfMemoryException when it hits the bmp.Clone line.
Any ideas as to what's happening, or perhaps a better solution to converting the image to B&W?
Here's some converted source code from this article:
Option Explicit On
Option Strict On
Public Class BitmapEncoder
''' <summary>
''' Copies a bitmap into a 1bpp bitmap of the same dimensions, fast
''' </summary>
''' <param name="b">original bitmap</param>
''' <returns>a 1bpp copy of the bitmap</returns>
Public Shared Function ConvertBitmapTo1bpp(ByVal b As System.Drawing.Bitmap) As System.Drawing.Bitmap
' Plan: built into Windows GDI is the ability to convert
' bitmaps from one format to another. Most of the time, this
' job is actually done by the graphics hardware accelerator card
' and so is extremely fast. The rest of the time, the job is done by
' very fast native code.
' We will call into this GDI functionality from C#. Our plan:
' (1) Convert our Bitmap into a GDI hbitmap (ie. copy unmanaged->managed)
' (2) Create a GDI monochrome hbitmap
' (3) Use GDI "BitBlt" function to copy from hbitmap into monochrome (as above)
' (4) Convert the monochrone hbitmap into a Bitmap (ie. copy unmanaged->managed)
Dim w As Integer = b.Width, h As Integer = b.Height
Dim hbm As IntPtr = b.GetHbitmap()
' this is step (1)
'
' Step (2): create the monochrome bitmap.
' "BITMAPINFO" is an interop-struct which we define below.
' In GDI terms, it's a BITMAPHEADERINFO followed by an array of two RGBQUADs
Dim bmi As New BITMAPINFO()
bmi.biSize = 40
' the size of the BITMAPHEADERINFO struct
bmi.biWidth = w
bmi.biHeight = h
bmi.biPlanes = 1
' "planes" are confusing. We always use just 1. Read MSDN for more info.
bmi.biBitCount = CShort(1)
' ie. 1bpp or 8bpp
bmi.biCompression = BI_RGB
' ie. the pixels in our RGBQUAD table are stored as RGBs, not palette indexes
bmi.biSizeImage = CUInt((((w + 7) And &HFFFFFFF8) * h / 8))
bmi.biXPelsPerMeter = 1000000
' not really important
bmi.biYPelsPerMeter = 1000000
' not really important
' Now for the colour table.
Dim ncols As UInteger = CUInt(1) << 1
' 2 colours for 1bpp; 256 colours for 8bpp
bmi.biClrUsed = ncols
bmi.biClrImportant = ncols
bmi.cols = New UInteger(255) {}
' The structure always has fixed size 256, even if we end up using fewer colours
bmi.cols(0) = MAKERGB(0, 0, 0)
bmi.cols(1) = MAKERGB(255, 255, 255)
'
' Now create the indexed bitmap "hbm0"
Dim bits0 As IntPtr
' not used for our purposes. It returns a pointer to the raw bits that make up the bitmap.
Dim hbm0 As IntPtr = CreateDIBSection(IntPtr.Zero, bmi, DIB_RGB_COLORS, bits0, IntPtr.Zero, 0)
'
' Step (3): use GDI's BitBlt function to copy from original hbitmap into monocrhome bitmap
' GDI programming is kind of confusing... nb. The GDI equivalent of "Graphics" is called a "DC".
Dim sdc As IntPtr = GetDC(IntPtr.Zero)
' First we obtain the DC for the screen
' Next, create a DC for the original hbitmap
Dim hdc As IntPtr = CreateCompatibleDC(sdc)
SelectObject(hdc, hbm)
' and create a DC for the monochrome hbitmap
Dim hdc0 As IntPtr = CreateCompatibleDC(sdc)
SelectObject(hdc0, hbm0)
' Now we can do the BitBlt:
BitBlt(hdc0, 0, 0, w, h, hdc, 0, 0, SRCCOPY)
' Step (4): convert this monochrome hbitmap back into a Bitmap:
Dim b0 As System.Drawing.Bitmap = System.Drawing.Bitmap.FromHbitmap(hbm0)
'
' Finally some cleanup.
DeleteDC(hdc)
DeleteDC(hdc0)
ReleaseDC(IntPtr.Zero, sdc)
DeleteObject(hbm)
DeleteObject(hbm0)
'
Return b0
End Function
Private Shared SRCCOPY As Integer = &HCC0020
Private Shared BI_RGB As UInteger = 0
Private Shared DIB_RGB_COLORS As UInteger = 0
<System.Runtime.InteropServices.DllImport("gdi32.dll")> _
Private Shared Function DeleteObject(ByVal hObject As IntPtr) As Boolean
End Function
<System.Runtime.InteropServices.DllImport("user32.dll")> _
Private Shared Function GetDC(ByVal hwnd As IntPtr) As IntPtr
End Function
<System.Runtime.InteropServices.DllImport("gdi32.dll")> _
Private Shared Function CreateCompatibleDC(ByVal hdc As IntPtr) As IntPtr
End Function
<System.Runtime.InteropServices.DllImport("user32.dll")> _
Private Shared Function ReleaseDC(ByVal hwnd As IntPtr, ByVal hdc As IntPtr) As Integer
End Function
<System.Runtime.InteropServices.DllImport("gdi32.dll")> _
Private Shared Function DeleteDC(ByVal hdc As IntPtr) As Integer
End Function
<System.Runtime.InteropServices.DllImport("gdi32.dll")> _
Private Shared Function SelectObject(ByVal hdc As IntPtr, ByVal hgdiobj As IntPtr) As IntPtr
End Function
<System.Runtime.InteropServices.DllImport("gdi32.dll")> _
Private Shared Function BitBlt(ByVal hdcDst As IntPtr, ByVal xDst As Integer, ByVal yDst As Integer, ByVal w As Integer, ByVal h As Integer, ByVal hdcSrc As IntPtr, _
ByVal xSrc As Integer, ByVal ySrc As Integer, ByVal rop As Integer) As Integer
End Function
<System.Runtime.InteropServices.DllImport("gdi32.dll")> _
Private Shared Function CreateDIBSection(ByVal hdc As IntPtr, ByRef bmi As BITMAPINFO, ByVal Usage As UInteger, ByRef bits As IntPtr, ByVal hSection As IntPtr, ByVal dwOffset As UInteger) As IntPtr
End Function
<System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)> _
Private Structure BITMAPINFO
Public biSize As UInteger
Public biWidth As Integer, biHeight As Integer
Public biPlanes As Short, biBitCount As Short
Public biCompression As UInteger, biSizeImage As UInteger
Public biXPelsPerMeter As Integer, biYPelsPerMeter As Integer
Public biClrUsed As UInteger, biClrImportant As UInteger
<System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst:=256)> _
Public cols As UInteger()
End Structure
Private Shared Function MAKERGB(ByVal r As Integer, ByVal g As Integer, ByVal b As Integer) As UInteger
Return CUInt((b And 255)) Or CUInt(((r And 255) << 8)) Or CUInt(((g And 255) << 16))
End Function
Private Sub New()
End Sub
End Class
Call it using:
Dim myFile = "c:\test.jpg"
Using Input As New Bitmap(myFile)
Using Output = BitmapEncoder.ConvertBitmapTo1bpp(Input)
Output.Save("c:\test.bmp")
End Using
End Using
GDI+ exception messages are pretty miserable, OutOfMemoryException can be raised in the Clone() method if the rectangle you pass is outside of the image bounds. Nothing to do with running out of memory. Which could easily happen here, it isn't that likely that the source bitmap is 1200 x 1800. Make your code look like this:
Dim bte() As Byte = System.Convert.FromBase64String(imgStr)
Dim ms As New IO.MemoryStream(bte)
Dim monoImage As Drawing.Bitmap
Using bmp As New Drawing.Bitmap(ms)
Dim rect As New Drawing.Rectangle(0, 0, bmp.Width, bmp.Height)
monoImage = bmp.Clone(rect, Drawing.Imaging.PixelFormat.Format1bppIndexed)
End Using
Not so sure the resulting bitmap would look good or is usable, GDI+ has poor support for indexed pixel formats. Win7 has a different version of gdiplus.dll than Windows 2003. I tested this code only on Win7.
Take a look at this: http://msdn.microsoft.com/en-us/library/system.windows.media.imaging.formatconvertedbitmap.aspx
But change PixelFormats.Gray32Float
to PixelFormats.BlackWhite
One problem I see right away is that your code has a resource leak:
Dim monoImage As Drawing.Bitmap = New Drawing.Bitmap(1200, 1800,
Drawing.Imaging.PixelFormat.Format1bppIndexed)
...
monoImage = bmp.Clone(rect, Drawing.Imaging.PixelFormat.Format1bppIndexed)
You're creating a brand-new bitmap and assigning it to monoImage
, and then almost immediately throwing it away without ever disposing of the original Bitmap
. If you're doing this often, you're leaking a lot of GDI resources and can receive all sorts of errors as a result (including OOMs).
Just move the declaration to the same line as the "new" assignment:
Dim monoImage As Drawing.Bitmap = bmp.Clone(rect,
Drawing.Imaging.PixelFormat.Format1bppIndexed)
You also need to make sure you're disposing the other Bitmap
, and the MemoryStream
, and so on and so forth; all of these implement IDisposable
so just wrap them in Using
.
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