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.NET Forum / .NET Framework / Compact Framework / February 2008Large image
Hi, I have a map in the format of 3000 * 3000 pixel bmp-file. This is of course to big to load into a bitmap. Does anyone have any ideas how to handle this image to be able to pan the map in the PDA. Do I have to cut the image into smaller pieces or is it somehow possible to read small parts of the image depending on which part of the map to be shown while panning? /Broeden . The easiest way would be to use a PictureBox control and set the scroll bars which will allow you to scroll the image. This depends on the size of the image (colour depth) as to whether your device will render it before it runs out of memory. If size (depth) is a problem, maybe divide the image up and draw "tiles" when required.  SignatureSimon Hart Visual Developer - Device Application Development MVP http://simonrhart.blogspot.com > Hi, > [quoted text clipped - 7 lines] > /Broeden > .. > If size (depth) is a problem, maybe divide the image up and draw "tiles" > when required. Yes, the size is the problem. I have thought about dividing the image into smaller images. But if it's possible I want to read parts of image directly from the imagefile or load the whole image into a byte array and than create selected parts of the image when needed. Is this possible? Is it possible to read parts of the image (bmp) via some sort of stream? /Broeden To do it directly is difficult becasue you have to look at the stride of the data and pull only parts of each scan line, essentially pulling just the data you want and assembling a new bitmap. Doable, but not fun. It's a lot easier to use an existing function like that which the native Imaging library provides. The CF doesn't directly have any wrappers for this stuff, but we'd done it in the SDF: http://blog.opennetcf.org/afeinman/CategoryView,category,SDF%202.0.aspx SignatureChris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com >> If size (depth) is a problem, maybe divide the image up and draw "tiles" >> when required. [quoted text clipped - 9 lines] > > /Broeden > The CF doesn't directly have any wrappers for this stuff, > but we'd done it in the SDF: > > http://blog.opennetcf.org/afeinman/CategoryView,category,SDF%202.0.aspx Thanks for your information! I'm new to OpenNETCF. What do I have to think about before using the SDF in my product? I'm using CF2.0 and VS2005. /Broeden Nothing. The community edition is free, so just download, install, add a reference and use. If you want Studio integration with toolbox support, help, templates and full source code then you can buy the SDF Extensions for Studio for a nominal fee. SignatureChris Tacke, Embedded MVP OpenNETCF Consulting Giving back to the embedded community http://community.OpenNETCF.com >> The CF doesn't directly have any wrappers for this stuff, >> but we'd done it in the SDF: [quoted text clipped - 9 lines] > > /Broeden > Nothing. The community edition is free, so just download, install, add a > reference and use. If you want Studio integration with toolbox support, > help, templates and full source code then you can buy the SDF Extensions for > Studio for a nominal fee. Thanks again! I have install the SDF and tested the samples. I have found out how to load parts of the image to get a thumbnail of the image. But is it possible to load for instance the upper left 1000*1000 pixels of a large image? /Broeden If I recall, you're working with BMP images. If that is the case, you can write a relatively simply method to read and decode the BMP into a Bitmap object. use SetPixel while testnig and LockBits to optimize. Hilton On 31 Jan, 14:58, "<ctacke/>" <ctacke[at]opennetcf[dot]com> wrote: > Nothing. The community edition is free, so just download, install, add a > reference and use. If you want Studio integration with toolbox support, > help, templates and full source code then you can buy the SDF Extensions > for > Studio for a nominal fee. Thanks again! I have install the SDF and tested the samples. I have found out how to load parts of the image to get a thumbnail of the image. But is it possible to load for instance the upper left 1000*1000 pixels of a large image? /Broeden The problem there is just trying to load a 3000x3000 bitmap is very likely to run the device out of memory long before it's fully in memory. SetPixel will be painfully slow if attempting to copy the data. It's probably better to just lock the destination bitmap and use copy methods to pull from a stream and write it into the scan0 ptr at an offset. SignatureChris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com > If I recall, you're working with BMP images. If that is the case, you can > write a relatively simply method to read and decode the BMP into a Bitmap [quoted text clipped - 17 lines] > > /Broeden This is a little new to me. Can you be a bit more specific? For instance, to simplify. How do I read half of a 2000 *2000 pixel bmp (2000 * 1000) into an bitmap object? Without first loading the whole image into the memory of course. /Broeden Well, you'll have to browse the web or buy a book and become familiar with the BMP format - it's a pretty brain dead format - hence its bad compression and then figure out what parts to read and 'decode' into bits, bytes, and pixels. The bottom line it that you are going to have to write the image reading code or buy it if anyone has something. If I have some time, I might be able to write it for you, but not before the end of April. Hilton > This is a little new to me. > [quoted text clipped - 4 lines] > > /Broeden Thanks Hilton for your reply! I found some articles on how to manipulate bitmaps on the Net to start with. What I'm now looking for is an example of how to select parts of the stream. For instance how could SkipEverySecondPixel be implemented? Stream stream = new Stream("test.bmp"); Stream newStream = SkipEverySecondPixel(Stream); bmp = new Bitmap(NewStream ); stream.Close(); newStream.Close(); /Broeden You have to use Seek on the source stream and manually calculate the offsets based on the image properties (bits per pixel, stride, etc). SignatureChris Tacke, eMVP Join the Embedded Developer Community http://community.opennetcf.com > Thanks Hilton for your reply! > [quoted text clipped - 13 lines] > > /Broeden If the BMP is compressed, you need to handle that too. Do this using streams; i.e. open the BMPStream using another stream (or filename). This BMPStream would have calls like "Color NextPixel", SkipPixels (int n), and "MoveToNextRow" etc; i.e. the code reading this stream should not care about how the BMP is compressed. If it made sense, you could add SkipRow(), you don't need SkipPixel since you could just call NextPixel and ignore what it returns. However, getting back to what you originally asked, you need to think about the new Bitmap (filename, x, y, cx, cy) call. If you can solve that, you're pretty much done. Hope that makes sense. Hilton > You have to use Seek on the source stream and manually calculate the > offsets based on the image properties (bits per pixel, stride, etc). [quoted text clipped - 16 lines] >> >> /Broeden Chris, > The problem there is just trying to load a 3000x3000 bitmap is very likely > to run the device out of memory long before it's fully in memory. Correct, that's why I said that he should write a "read and decode" method, essentially the equivalent of "new Bitmap (filename, x, y, cx, cy)". > SetPixel will be painfully slow if attempting to copy the data. It's > probably better to just lock the destination bitmap and use copy methods > to pull from a stream and write it into the scan0 ptr at an offset. Right, that's why I suggested to use SetPixel while testing (i.e. just get it working), then use LockBits (i.e. scan0) to optimize, unless using scan0 initially would be best although i doubt it given the number of BMP formats, pixel depths, etc. Hilton >> If I recall, you're working with BMP images. If that is the case, you >> can write a relatively simply method to read and decode the BMP into a [quoted text clipped - 17 lines] >> >> /Broeden Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. 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