.NET (Core and Framework)

Re: Resize a monochrome bitmap without using any class

19-May-10 14:55

You can't run anything under .NET without using some .NET classes, so I'll assume the classes you want to avoid are the graphical ones only. Then this is the recipe:

1. study the specification of your input image format, maybe it is a BMP file;
2. read the input, probably into a byte array;
3. now turn it into some in-memory representation that you feel comfortable with;
4. perform the resize, i.e. create a new bitmap in memory
5. study the specification of your output image format, maybe it is a PNG file;
6. generate your output image by converting it into the output format.

You probably could combine some of the steps. You will need a lot of bit manipulations, so make sure you are fluent in masking, shifting, and the like. For the resizing itself, you may choose a nearest-neighbor approach, or alternatively you may want to study different interpolation algorithms, bi-cubic is popular.

If you need an extra challenge, you may implement compression, e.g. the one used in the JPEG file format.

The alternative to all of the above is less than 10 lines of code, based on the Bitmap class.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

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Mehdi Ghiasi20-May-10 2:06

Mehdi Ghiasi

20-May-10 2:06

No! I have a monochrome bitmap in an integer array table and I want to resize it into a new array WITHOUT GDI+ or any Class that Resizes the image For me. I want to know How It Works!

Regards.

Mehdi Ghiasi

Re: Resize a monochrome bitmap without using any class

Luc Pattyn20-May-10 2:19

Re: Resize a monochrome bitmap without using any class

20-May-10 2:19

The result probably won't look very good under these conditions; here are two examples (data in binary):

1.
an image with a width of 8 pixels, one row containing

00101110

scaled up by a factor of 2, it becomes

0000110011111100
0000110011111100

So the result is a "pixelated" image, bits just got replicated, as there is no extra information available.

2.
the reverse operation: an image with a width of 16 pixels, two rows containing

0x0x1x0x1x1x1x0x
xxxxxxxxxxxxxxxx

(you can put a 0 or 1 at any of the 'x' positions) scaled down by a factor of 2 it could become

00101110

which again does not look anywhere near the same as the original as 75% of the information got thrown away.

And that was only the very simple case of a scale by 1/2 or 2/1.

As I said before, you will need a lot of bit manipulations, so make sure you are fluent in masking, shifting, and the like. For the resizing itself, you may choose a nearest-neighbor approach.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

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Mehdi Ghiasi20-May-10 7:18

Mehdi Ghiasi

20-May-10 7:18

So how can I scale a 100x100 image into 150x150 ?

Regards.

Mehdi Ghiasi

Re: Resize a monochrome bitmap without using any class

Thomas Krojer21-May-10 4:08

Thomas Krojer

21-May-10 4:08

only double even OR odd bits ...

Re: Resize a monochrome bitmap without using any class

T M Gray21-May-10 5:24

T M Gray

21-May-10 5:24

I want to answer you, but I want to do it without using any words or code. If you get my telepathic message you should be all set.

Accepting a rejected character in a Masked Textbox

gmhanna18-May-10 1:58

gmhanna

18-May-10 1:58

Hi,

I'm trying to figure out how to accept a rejected character in a masked text box. I am using a "Masked Textbox" for the person's last name and to ensure all alpha characters, I'm using "L?????????????????", however if the person's last name has a quote in it, the masked text box is rejecting it but in code I want to accept it. I see I can where I can check the character in the Reject event, however I can not cancel the reject.

Any suggestions how to do this, other than using a Keydown event and accepting only the characters I want?

Thank you,

Glenn

Re: Accepting a rejected character in a Masked Textbox

Peace ON18-May-10 2:42

Peace ON

18-May-10 2:42

If you want to allow single quote or double quote then use
C instead of ?.

It will allow any printable character.
http://msdn.microsoft.com/en-us/library/system.windows.forms.maskedtextbox.mask.aspx[^]

Otherwise, you need to do validation/restriction on last name manually.
Either by tracking lost focus event or likewise..

Hope this will help!

Jinal Desai - LIVE
Experience is mother of sage....

Advanced .NET cource

marca29217-May-10 19:56

marca292

17-May-10 19:56

Hi,

I am looking for advanced .NET cources. Cources in architecture, performance and debug difficult problems (using WinDbg, Adplus) and similar cources. Do you know a good course center?

Best Regards
Mac

Richard MacCutchan17-May-10 21:26

Richard MacCutchan

17-May-10 21:26

You could have looked here[^] first.

It's time for a new signature.

marca29217-May-10 22:18

marca292

17-May-10 22:18

Thanks for that brilliant answer. Obviously you don't have participate at a good course that you can recommended.

Thanks for your help Ruchard MecCutchan!

Richard MacCutchan18-May-10 10:59

Richard MacCutchan

18-May-10 10:59

marca292 wrote:
Thanks for your help Ruchard MecCutchan!

Maybe you should start with the advanced copy & paste, followed by the introduction to spelling. Laugh | :laugh:

It's time for a new signature.

Luc Pattyn18-May-10 1:19

18-May-10 1:19

These may or may not paas your "good course" criterium:

MSDN: the Beginner Developer Learning Center
http://msdn.microsoft.com/en-us/beginner/default.aspx

MSDN Channel 9
http://channel9.msdn.com/learn/

100 courses
http://www.onlinecourses.org/2009/10/28/100-incredible-open-courses-for-the-ultimate-tech-geek/

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

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Render Method

Mountainking0217-May-10 8:37

Mountainking02

17-May-10 8:37

Hi, i am programming a CAD like application (2D) and i am wondering about how to do the rendering. I have a canvas for the drawing. My intention was to use the ZIndex from the canvas for multi layer support. For lines, rectangles and so on i have created custom shapes.
But now to the problems. If any shape is overlapping another one the overlapped region appears darker (when opacity < 1). This effect i would like to prevent. The shapes of an whole layer should be a homogenous drawing without visible overlapping.

I tried using Pathgeometry instead, but in this case every LineSegment or PathFigure is rendered equal and i can't set different brushes or dashes for example. How could i solve this?

The other Problem: I want to put visual objects on the Canvas which persists of several other lines, rectangles and so on. Each of this geometries should have its on brush and ZIndex. How could i represent such an object? A shape is not working due to the fact i can't set different brushes, as well as different ZIndices doesn't work.

Ok i could add the geometries of that objects directly to the Canvas, but it would be nicer to have them stored as an object. Any ideas to achieve this?

Luc Pattyn17-May-10 8:58

17-May-10 8:58

this is what I would do:

- define a base class, "DrawingShape"; it has some properties including a Z-order (or a Layer) and some methods, including a Draw() method.
- define specialized shape classes, deriving from DrawingShape; they each override the Draw() method.
- for a drawing, define a List<DrawingShape>
- order that list according to Z-order (back to front).
- to paint the drawing (e.g. in the Paint handler of your canvas Panel), do a foreach over the ordered list of shapes, and call their Draw() method.

A lot of extras are possible; one would be a ShapeGroup, which itself is a DrawingShape, and holds a list of DrawingShapes; so it gets added as one item to the drawing, and its Draw() method would call the Draw() method of all its internal DrawingShapes.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

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Mountainking0220-May-10 4:48

Mountainking02

20-May-10 4:48

I have thought about that solution too, but doing it this way raises some new problems. E.g. Hittesting.
Can you go a bit deeper on how to render exactly, especially on the ShapeGroup Drawing-Method. Shall i use the Shape, Path or StreamGeometry class for rendering? And i don't see how to apply for example different DashStyles to the Lines inside the ShapeGroup Drawing-Method.

Luc Pattyn20-May-10 5:14

20-May-10 5:14

Hi,

1. rendering
depends on your environment. in WinForms, use Graphics.DrawLine() and the like. In other environments, use whatever is appropriate.

2. hit testing
in my view hit testing takes a method, maybe an int HitTest(Point p), which exists in the base class, and needs to be overridden by the specialized shapes. There are many ways to implement it, it depends on what you want to call a hit. Here is one I like a lot, although it isn't the easiest one:

- it basically calculates the distance from the mouse position (the Point parameter) to the nearest segment of the shape, and returns that.
- it gets called for all shapes, and the closest one wins, with an upper bound on the distance.
This works very comfortably for the user, as there is no need to exactly hit a line, and it allows to "see through" hollow shapes, so you can hit a small circle overlayed by a large hollow (i.e. unfilled) rectangle.

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

I only read formatted code with indentation, so please use PRE tags for code snippets.

I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).

Mountainking0220-May-10 5:48

Mountainking02

20-May-10 5:48

Ok, but remember, i wanted to avoid overlapping effects. For example look at the following code:

Path path = new Path();<br />
            path.Stroke = Brushes.IndianRed;<br />
            path.StrokeThickness = 0.05;<br />
            path.Opacity = 0.5;<br />
            GeometryGroup geometryGroup = new GeometryGroup();<br />
<br />
            for (int i = 0; i < 5000; i++)<br />
            {<br />
                PathGeometry pathGeometry = new PathGeometry();<br />
                PathFigure pathFigure = new PathFigure();<br />
                pathFigure.StartPoint = new Point(rand.Next(0, 50), rand.Next(0, 50));<br />
                pathFigure.Segments.Add(new LineSegment(new Point(rand.Next(0, 50), rand.Next(0, 50)), true));<br />
                pathGeometry.Figures.Add(pathFigure);<br />
                geometryGroup.Children.Add(pathGeometry);<br />
            }<br />
<br />
            path.Data = geometryGroup;<br />
            Children.Add(path);

I can't set the brush or dashstyles individually to a Line. Only setting the "global" path values is possible, so that each Line is rendered equal. Thats my problem. I can take all the code inside the for loop, but then i have the overlapping effekt again.

Luc Pattyn20-May-10 6:07