.net Wrapper for DrawPageToIStream

[DolphinMann]

Does anyone have the .net wrapper for the DrawPageToIStream function? I couldn't find it anywhere in the examples but it is mentioned in the documentation and many different threads.

[Ivan - Tracker Software]

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       [StructLayout(LayoutKind.Sequential, Pack = 1)]
        public struct PXV_DrawToImageParams
        {
            public Int32 ImageFormat;
            public Int32 Flags;  // see PXV_DrawToImageFlags
            public Int32 Bpp;
        };

        public enum PXV_DrawToImageFlags
		{
			pxvdif_None						=	0x0000,
		};


        [DllImport("pxcview")]
        public static extern int PXCV_DrawPageToIStream(IntPtr hDoc,
        												Int32 page_num,
        												ref PXV_CommonRenderParameters pParams,
        												Int32 backColor,
        												ref PXCV_DrawPageToIStream pImageParams,
        												ref IStream pStream);

Where IStream is an object with IStream interface (http://msdn.microsoft.com/en-us/library ... -snippet-1).

[DolphinMann]

Thank you for that. I am probably overlooking something obvious, but I just can't seem to make this work. I keep getting an error during the DLL call that I am attempting to read/write protected memory. I'm pretty sure it's my iStream memory but I can't be positive.

I was previously using DrawPageToDIB and was working, but I'd like to use the IStream version for the additional features of built-in formatting and built in pixel depth;

This was my old code( I didn't include the document/library initialization, nothing has changed there and it's outside of this block), and pretty much stripped from your examples:

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IntPtr hBase = IntPtr.Zero;
                        PXCV_Lib36.PXV_CommonRenderParameters crp = new PXCV_Lib36.PXV_CommonRenderParameters();
                        int[] rect = { 0, 0, width, height };
                        int size = Marshal.SizeOf(rect[0]) * rect.Length;
                        IntPtr rectPointer = Marshal.AllocHGlobal(size);
                        Marshal.Copy(rect, 0, rectPointer, 4);

                        crp.WholePageRect = rectPointer;
                        crp.Flags = (int)PXCV_Lib36.PXV_CommonRenderParametersFlags.pxvrpf_None;
                        crp.RenderTarget = PXCV_Lib36.PXCV_RenderMode.pxvrm_Exporting;
Int32 clr = aBkgColor.ToArgb();
IntPtr hBitmap = IntPtr.Zero;

PXCV_Lib36.PXCV_DrawPageToDIBSection(m_Doc, page, ref crp, hBase, clr, ref hBitmap, IntPtr.Zero, 0)
                        aBitmap = Image.FromHbitmap(hBitmap);
            DeleteObject(hBitmap);

new code that I can't get to work, I took the IStreamWrapper from one of the examples provided and you can see two commented out lines where i was trying to initialize a pointer from file or memory block directly, I could not get that to work either

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                        IntPtr hBase = IntPtr.Zero;
                        PXCV_Lib36.PXV_CommonRenderParameters crp = new PXCV_Lib36.PXV_CommonRenderParameters();
                        int[] rect = { 0, 0, width, height };
                        int size = Marshal.SizeOf(rect[0]) * rect.Length;
                        IntPtr rectPointer = Marshal.AllocHGlobal(size);
                        Marshal.Copy(rect, 0, rectPointer, 4);

                        crp.WholePageRect = rectPointer;
                        crp.Flags = (int)PXCV_Lib36.PXV_CommonRenderParametersFlags.pxvrpf_None;
                        crp.RenderTarget = PXCV_Lib36.PXCV_RenderMode.pxvrm_Exporting;

                        PXCV_Lib36.PXV_DrawToImageParams dip = new PXCV_Lib36.PXV_DrawToImageParams();
                        dip.Flags = (int)PXCV_Lib36.PXV_DrawToImageFlags.pxvdif_None;
                        if (!useColor)
                        {
                            dip.Bpp = 1;
                        }
                        else
                        {
                            dip.Bpp = 24;
                        }

                        dip.ImageFormat = 0x54494646;
Int32 clr = backColor.ToArgb();

                        Stream stream = new MemoryStream();
                        IStream iStream = new IStreamWrapper(stream);
                        //CreateStreamOnHGlobal(IntPtr.Zero, true, out iStream);
                        //SHCreateStreamOnFile("temp.tif", StgmConstants.STGM_CREATE | StgmConstants.STGM_READWRITE, ref iStream);
                        [b]PXCV_Lib36.PXCV_DrawPageToIStream(m_Doc, page, ref crp, clr, ref dip, ref iStream)[/b]
                        System.Runtime.InteropServices.ComTypes.STATSTG stat;
                        iStream.Stat(out stat, 1);
                        long bufferSize = stat.cbSize;
                        byte[] buffer = new byte[bufferSize];
                        stream.Write(buffer, 0, buffer.Length);
                        stream.Flush();
                        returnValue = new Bitmap(stream);
                        stream.Close();

I die on the bold line with memory access every time

[Will - Tracker Supp]

Hi DolphinMann,

The bold tags are stripped when using the code tags. Could you point us to the specific line that's killing you?

Cheers,

[DolphinMann]

PXCV_Lib36.PXCV_DrawPageToIStream(m_Doc, page, ref crp, clr, ref dip, ref iStream)

That is where I get the access violation. As i said I think it has something to do with my iStream since I had this working with the DrawToDIB, though I suppose there is an issue with my Image params, but I cut and paste that from your code block.

[DolphinMann]

Does anyone else watching the forums have a .NET sample code using the DrawPageToIStream?

[Ivan - Tracker Software]

I'm working on a sample for you. As I'm not experienced with C# it takes time.
In my sample I will use SHCreateStreamOnFileEx function (http://msdn.microsoft.com/en-us/library ... s.85).aspx) instead of the wrapper.

[Ivan - Tracker Software]

Here is a sample code that works fine on my side:

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		[DllImport("Shlwapi.dll")]
		public static extern int SHCreateStreamOnFile(string pszFile, Int32 grfMode, out IStream ppstm);

		private void saveToPNGToolStripMenuItem_Click(object sender, EventArgs e)
		{
			if (m_PDFDoc == null)
				return;


            IStream aIStream;
			Color bgColor;

			PXCV_Lib36.PXV_CommonRenderParameters aCommonRenderParam = new PXCV_Lib36.PXV_CommonRenderParameters();
			PXCV_Lib36.PXV_DrawToImageParams aImageParams = new PXCV_Lib36.PXV_DrawToImageParams();

			PageDimension aPageDim;
			Size aPageSize = Size.Empty;
			PXCV_Helper.RECT aWholePage = new PXCV_Helper.RECT();

			IntPtr p1 = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(PXCV_Helper.RECT)));

			try
			{
				int res = SHCreateStreamOnFile("e:\\sample.png", 0x1042, out aIStream);

				m_PDFDoc.GetPageDimensions(this.pdfViewCtl1.PageNumber, out aPageDim.w, out aPageDim.h);
				aPageSize.Width = (int)(aPageDim.w * 96.0 / 72.0);
				aPageSize.Height = (int)(aPageDim.h * 96.0 / 72.0);
				aWholePage.left = 0;
				aWholePage.top = 0;
				aWholePage.right = aPageSize.Width;
				aWholePage.bottom = aPageSize.Height;

				Marshal.StructureToPtr(aWholePage, p1, false);

				aCommonRenderParam.WholePageRect = p1;
				aCommonRenderParam.DrawRect = System.IntPtr.Zero;
				aCommonRenderParam.RenderTarget = PXCV_Lib36.PXCV_RenderMode.pxvrm_Exporting;
				aCommonRenderParam.Flags = 0;

				aImageParams.Bpp = 32;
				aImageParams.ImageFormat = 0x504e4720;

				// aImageParams.Bpp = 1;
				// aImageParams.ImageFormat = 0x54494646;

				aImageParams.Flags = (int)PXCV_Lib36.PXV_DrawToImageFlags.pxvdif_None;

				bgColor = Color.FromArgb(0, 0, 0, 0);

				m_PDFDoc.DrawToIStream(aIStream, this.pdfViewCtl1.PageNumber, aCommonRenderParam, aImageParams, bgColor);
			}
			finally
			{
				Marshal.FreeHGlobal(p1);
			}
		}

SHCreateStreamOnFileEx does not work properly for some reason - stream is created, all functions work ok, but file was not created.
But I found that SHCreateStreamOnFile works fine.

[DolphinMann]

Thank you for that code snippet, it was very helpful however I am still a bit stuck. I think it because I am not working with the correct version of the pxcview.dll or the correct PXCV_Lib.cs file(.net wrapper)

The code you have the following line:
m_PDFDoc.DrawToIStream

Is the m_PDFDoc variable supposed to be a PDFDoc value as defined in the PXCV_Lib.cs file from the examples?

And is this the right reference to the pxcview.dll?

[DllImport("pxcview.dll")]
public static extern int PXCV_DrawPageToIStream(IntPtr hDoc,
Int32 page_num,
ref PXV_CommonRenderParameters pParams,
Int32 backColor,
ref PXV_DrawToImageParams pImageParams,
ref IStream pStream);

[Ivan - Tracker Software]

Here is my sample.

[DolphinMann]

Thank you, that worked. My wrapper function was passing a ref to the IStream, not the actual IStream like you had in your example. Thank you!

[DolphinMann]

One small note, it looks like you never release the iStream variable so the saved image cannot be viewed or modified until the executing application is close.

I cannot find any istream.close/dispose/release functions however. What is the best way to go about closing that stream so the file can be accessed?

[Vasyl-Tracker Dev Team]

Code: Select all

IStream aIStream;

- it defines smart-pointer to 'classic' IStream. The .NET's garbage-collector knows about that and will automatically release it a bit later, after using. Also you may release it immediately by:

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System.Runtime.InteropServices.Marshal.ReleaseComObject(aIStream);

HTH

[michael wagmann]

I've downloaded and run your sample code.
Unfortunatly, it seems that the bpp property of PXV_DrawToImageParams does not work correctly. In case of PNG(imageformart = 0x504e4720) a value of 8 is ignored and an image with 24 bpp is created. When bpp is set to 1, than a png image file with 1bpp is created, so in principle the code works.
According to the documentation of PXV_DrawToImageParams it is possible to export 8bpp PNG files. [ https://help.pdf-xchange.com/DEV/de ... mageparams ]
Can you please have a look into your library code? We need to export pdf files as 8bpp png files. Btw, in case of JPG 8 bpp doesn't work, too.

[Tracker Supp-Stefan]

Hello Michael,

I've asked Ivan to take a look at this again, and he will advise as soon as he can.

Regards,
Stefan

[Ivan - Tracker Software]

That function can produce the following PNG files:

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====================================================================================
|  PNG type        | PXV_DrawToImageParams.bpp | PXV_CommonRenderParameters.Flags  |
====================================================================================
|  1 bpp B&W       |             1             | pxvrpf_BlackAndWhite              |
|  1 bpp mono      |             1             |                                   |
|  8 bpp gray      |             8             | pxvrpf_BlackAndWhite              |
|  16 bpp alphgray |            16             | pxvrpf_BlackAndWhite              |
|  32 bpp ARGB     |            32             |                                   |
|  24 bpp RGB      |       -------- all the rest combinations --------             |
====================================================================================

HTH

[michael wagmann]

Ok. Can you tell me where to find the value of the pxvrpf_BlackAndWhite constant? In the online documentation of PXV_CommonRenderParameters I can not find it [https://help.pdf-xchange.com/DEV/de ... parameters}.

[Tracker Supp-Stefan]

Hi Michael,

I've passed that latest question to Ivan and he will post here shortly.

Regards,
Stefan

[Ivan - Tracker Software]

Yes, as I see two flags are undocumented. Will fix that on the help system, and also provide them here:

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====================================================================================
| pxvrpf_BlackAndWhite | 0x0080 | If set, a task will be rendered in black&white   |
|                      |        | mode. Has meaning for PXCV_DrawPageToDC and      |
|                      |        | PXCV_DrawPageToIStream methods                   |
| pxvrpf_Dither        | 0x0100 | Has meaning only with pxvrpf_BlackAndWhite flag  |
====================================================================================

[michael wagmann]

Hi Ivan,

I've set the flags property of the CommonRenderParametersFlags to the blackandwhite value (0x0080) and the bpp value of the DrawToImageParams to a value of 8.
Unfortunatly, the PXCV_DrawPageToIStream function fails in that case.

After having a closer look at the values of the PXV_CommonRenderParametersFlags enumeration, I used 0x0008 instead of 0x0080 and a grayscale PNG was created. However, still with 24 bpp even though bpp was set to a value of 8.

Your post from 27. Nov. indicates that there is no combination of BPP and CommonRenderParameter-Flags to produce an image with 8bpp and color. Is that correct? The Viewer is able to do so.

Can you please enhance your "pxcv_sample", so that I have a running example?

BR, Simon

[Ivan - Tracker Software]

I see that the combination of BPP=8 and pxvrpf_BlackAndWhite flag cause an error.

I have fixed that issue and also add support for 8bpp color images. Now the table will look like:

Code: Select all

==============================================================================================
|  PNG type        | PXV_DrawToImageParams.bpp | PXV_CommonRenderParameters.Flags            |
==============================================================================================
|  1 bpp B&W       |             1             | pxvrpf_BlackAndWhite                        |
|  1 bpp mono      |             1             |                                             |
|  8 bpp gray      |             8             | pxvrpf_BlackAndWhite or pxvrpf_RenderAsGray |
|  8 bpp palette   |             8             |                                             |
|  16 bpp alphgray |            16             | pxvrpf_BlackAndWhite or pxvrpf_RenderAsGray |
|  32 bpp ARGB     |            32             |                                             |
|  24 bpp RGB      |       -------- all the rest combinations --------                       |
==============================================================================================

These changes will be available in a next build.