How to load the image from a dwg file?

[Spencer-reborn-Elliott]

Firstly, congratulations on moving the library from pre-release to release! Last time I was here it was in a much earlier phase.

Is there an easy way to extract or load the image inside a .dwg file? I tried a few other libraries and one in particular was extremely easy to load the image, then I could easily load the image into a Windows.Forms.PictureBox.

//Using Aspose
string dwgPathToFile = MyDir + "Drawing11.dwg";
CadImage cadImage1 = (CadImage)Image.Load(dwgPathToFile);

Trouble is, this is the only advantage (for myself) that the other library has - The ACadSharp library currently does everything else I want it to with ease, and is faster.

[DomCR]

Hi @Spencer-reborn-Elliott,

Do you mean the Preview of the file? or an image inserted in it?

If is the preview there is a conversation about it:

• DWGWriter thumbnail support #558

[Spencer-reborn-Elliott]

Hi @Spencer-reborn-Elliott,

Do you mean the Preview of the file? or an image inserted in it?

If is the preview there is a conversation about it:

* [DWGWriter thumbnail support #558](https://github.com/DomCR/ACadSharp/issues/558)

@DomCR thank you very much for the reply, it's very appreciated!

I'm not exactly familiar with AutoCAD or working with CAD files at all - I am not even familair with the process the user is following to create their dwg file. I believe they are starting with a rasterised image and importing that, then over-laying a bunch of layers and entities per layer over that raster image.

What I want to be able to achieve is generate an image that uses this base rasterised image embedded in the dwg file, with the layers (the visible layers anyway) over the image and then put this image into a windows form PictureBox. From there, I will then generate a pdf of this.

As a side note I just realised through looking at that link that you have a library for pdf's - I just implemented this with PdfSharp, but will seek to migrate to ACadSharp.PDF. Can't believe I overlooked that!

I am not sure if the preview is able to do this? The Utility I am building makes some changes to the layers in the CAD document (basically allows a user to make the layers visible or not and then save the file).

If I save the file after the changes are made, and then try to read the preview would that work? Probably not I guess, it's likely far too small? - I want to be able to print this to PDF as A3 size (420mmx297mm).

Regardless, I'd quite like to use the preview in the utility - I think it would be useful.

` void generatePreview()
{
if (selectDWGfile.FileName.Length > 0)
{
string path = selectDWGfile.FileName;
try
{
DwgPreview preview;
using (DwgReader reader = new DwgReader(path))
{
doc = reader.Read();
preview = reader.ReadPreview();
}

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, toolName);
            }
        }
        else
        {
            MessageBox.Show("Select a file first.", toolName);
        }
    }`

How would I convert the variable DwgPreview preview to a System.Drawing.Image or png etc? FromStream or something?

I really hope I am able to generate a large enough image, it would be so, so useful to me to be able to batch process hundreds of the dwg files and just export the images to pdf.

[DomCR]

As a side note I just realized through looking at that link that you have a library for pdf's - I just implemented this with PdfSharp, but will seek to migrate to ACadSharp.PDF. Can't believe I overlooked that!

ACadSharp.PDF is still in alpha but you can follow the updates and use it as it goes, if there is something that you would like to have priority just post an issue in the repo and I'll take a look.

I am not sure if the preview is able to do this? The Utility I am building makes some changes to the layers in the CAD document (basically allows a user to make the layers visible or not and then save the file).

Right now the Preview PR in ACadSharp can read the Preview section from a dwg file that has been generated by some other software, but still cannot generate its own, there also another option which is SVG, there is a PR for that too, that maybe you are able to extract an image from that but that's also in development.

How would I convert the variable DwgPreview preview to a System.Drawing.Image or png etc? FromStream or something?

Check the method save:
https://github.com/DomCR/ACadSharp/pull/563/files#diff-d4d8a0b8e6b9047ac1f527d60e1d2178edc7384f54ff63f2b32459f71300cfe8R28

Here it creates a png from the preview, for how to generate a System.Drawing.Image, I don't know how to do it on top of my head.

Hope this helps!

[Spencer-reborn-Elliott]

As a side note I just realized through looking at that link that you have a library for pdf's - I just implemented this with PdfSharp, but will seek to migrate to ACadSharp.PDF. Can't believe I overlooked that!

ACadSharp.PDF is still in alpha but you can follow the updates and use it as it goes, if there is something that you would like to have priority just post an issue in the repo and I'll take a look.

I am not sure if the preview is able to do this? The Utility I am building makes some changes to the layers in the CAD document (basically allows a user to make the layers visible or not and then save the file).

Right now the Preview PR in ACadSharp can read the Preview section from a dwg file that has been generated by some other software, but still cannot generate its own, there also another option which is SVG, there is a PR for that too, that maybe you are able to extract an image from that but that's also in development.

How would I convert the variable DwgPreview preview to a System.Drawing.Image or png etc? FromStream or something?

Check the method save: https://github.com/DomCR/ACadSharp/pull/563/files#diff-d4d8a0b8e6b9047ac1f527d60e1d2178edc7384f54ff63f2b32459f71300cfe8R28

Here it creates a png from the preview, for how to generate a System.Drawing.Image, I don't know how to do it on top of my head.

Hope this helps!

@DomCR Thank you very much for the reply, I appreciate your time taken in writing this.

Sadly, even if I incorporated the pull request, it looks like at best I would be able to generate the original saved preview (if any existed), but it wouldn't reflect any changes I made to the file - Which is the crucial part, as I am editing some entities and turning some other layers on/off.

Besides, I think maybe the preview isn't the best way to be trying to do this anyway - The preview muct surely be quite small and I need to be able to print this to PDF as a large format.

What I really need is to create a large image based on the DWG file, i.e Overlay all the entities on the active layers and create an image. - Basically, what a regular CAD program would visually render to the end user based on the current settings.

I think this may be a way off (or possibly not the intention of this library)? I am possibly asking for something that isn't on the roadmap or is a tonne of work?

I was a bit confused because I saw "ImageDefinitions" and tried the following:

`try
{
CadDocument doc = DwgReader.Read(path);

logIt("Image Count: " + doc.ImageDefinitions.Count().ToString());

foreach (ImageDefinition Image in doc.ImageDefinitions)
{
    logIt("Text: " + Image.FileName.ToString());
    logIt("Text: " + Image.ClassVersion.ToString());
}

}
catch (Exception ex)
{
MessageBox.Show(ex.Message, toolName);
}`

Believing that it may contains the images, as I saw a summary "// The collection of all images in the drawing.", but my code reveals that there are no images in the drawing (even though I know for sure that there is a raster image embedded inside it at a minimimum).

I was hoping it may generate an image of the DWG files current "view" if it was opened in a regular CAD file viewer, but even if it just exposed the raster image then at least there would be some hope that I could render the entitites on the visible layers myself (a rather lofty goal for myself to be honest and quite unlikely to achieve).

[Spencer-reborn-Elliott]

I also tried to use ACADSharp.PDF but I received an exception erorr when using this code:

try
{
    doc = DwgReader.Read(path);

    string filename = Path.ChangeExtension(path, ".pdf");
    PdfExporter exporter = new PdfExporter(filename);

    //Add the model space as a page
    exporter.Add(doc.ModelSpace);

    //Save and close the pdf
    exporter.Close();

}
catch (Exception ex)
{
    MessageBox.Show(ex.Message, toolName);
}

It returned "The method or operation is not implemented" and proceeded to create a 0 byte sized pdf file.

[DomCR]

The package hasn't been updated and the options are really limited, apologies for that.

I'm thinking of the best way to have this feature working as soon as possible, giving that has been requested multiple times.

One of the options is to generate a SVG and the user can create an image using an external library to create the thumbnail image,

For the ACadSharp.Pdf it would take more time to develop, in particular the text is really tricky to handle.

I'll try to keep you posted on the development.

[Spencer-reborn-Elliott]

The package hasn't been updated and the options are really limited, apologies for that.

I'm thinking of the best way to have this feature working as soon as possible, giving that has been requested multiple times.

One of the options is to generate a SVG and the user can create an image using an external library to create the thumbnail image,

For the ACadSharp.Pdf it would take more time to develop, in particular the text is really tricky to handle.

I'll try to keep you posted on the development.

@DomCR again, thank you so much for your time in replying. I am extremely grateful to hear that you are considering working on something that might enable what I am trying to achieve and eagerly awaiting any news on the development.

I cannot imagine the time it will save being able to batch process .DWG files and generating .pdf's of the drawing.

[DomCR]

Hi @Spencer-reborn-Elliott

I've released a new version for ACadSharp.Pdf, I've also added a new extension for CadDocument to generate the preview images and save them into the dwg file.

Here is a documentation of how to add the DwgPreview:

https://github.com/DomCR/ACadSharp/blob/master/docs/CadWriterDocs.md

I still have to write the documentation for the ACadSharp.Pdf but is as easy as using the preview created by the method CreatePreview.

Hope this helps!

[Spencer-reborn-Elliott]

@DomCR Thank you very much for including this in v1.1,6!

I have been very ill recently and didn't see this comment until now - Apologies for the late reply.
I thought I would try to simply do this as a test:

                    DwgPreview preview = doc.CreatePreview();
                    preview.Save("test.png");

Sadly, before the code reaches preview.Save there are errors on all of the different DWG files I tried. For example:

File 1 produced the error:
An error occurred while parsing EntityName. Line 32155, position 118.

File 2 produced the error:
Cannot process SVG file, cannot allocate the required memory

File 3 didn't produce an error, but it just sat in a seemingly never ending loop for what felt like 10 minutes before I called it.

However, some fantastic news! The update to ACadSharp.PDF means that the following code is now producing PDF files successfully!

                try
                {
                    string filename = Path.ChangeExtension(selectDWGfile.FileName, ".pdf");
                    PdfExporter exporter = new PdfExporter(filename);

                    //Add the model space as a page
                    exporter.AddModelSpace(doc);
                    
                    //Add each paper layout as a page
                    exporter.AddPaperLayouts(doc);

                    //Save and close the pdf
                    exporter.Close();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, toolName);
                }

Which is really very simple and easy to use, amazing!

I do really need to work out how to resize the PDF though, as the file produced is the same as the model space at a laughable 86 metres wide and 133 metres tall (I do mean metres, too).

It would be incredible to have a method to do this on the PdfExporter itself, otherwise I guess I am going to need to look at doc.ModelSpace.Layout.PaperSize or something like that in the modelspace or payout to resize it before using .AddModelSpace and .AddPaperLayouts? Not quite sure how to resize it.

Also, the pdf produced is doing something very weird with fonts on the paperlayouts - There's massive writing going across the page.

[DomCR]

Hi @Spencer-reborn-Elliott,

About the preview, could you share any of these flawed files so I can run the code on my end? It would be the best way to test the code.

Pdf export: when adding the modelspace, exporter.AddModelSpace(doc);, it takes the actual size, but if you add a paper Layout, it should have the size of the paper in it.

Text in the pdf: the text is a placeholder right now, there is no rotation or font applied and it seems that it would be the main problem of the pdf export. The temporal option that I'm exploring right now is to create a pdf based on the svg, which is easier to configure the fonts and text location.

[Spencer-reborn-Elliott]

@DomCR Sure thing, do you have an email address or something I can send them too?

The paper layout is coming out at the size configured, which is way more usable - Thank you.

I wondered what was happening with the text, it was gigantic and non-sense. Good luck with the svg, I will be following with acute interest! :-)

[DomCR]

Hi @Spencer-reborn-Elliott,

I shared a public email in my profile.

[Spencer-reborn-Elliott]

Hi @Spencer-reborn-Elliott,

I shared a public email in my profile.

Thank you very much - I have sent you a mail with the files!