Develop Reference

How to display pixels 1:1 in a PictureBox

I have a bitmap (from a .bmp file) that is actually a small part of a larger screen dump that I took earlier.
Now I want to display that bitmap in a PictureBox control (WinForms), but I have trouble getting it to display at the same ratio as when it was captured originally.
I assume it has something to do with Windows' DPI setting for my monitor, but how can I shortcut that and make the bitmap be displayed exactly as when captured?

I figured it out! The problem was not WinForms, but the horizontal and vertical resolution associated with the displayed bitmap. When copying the part of the original screendump into a new bitmap (the one that is later assigned to the Image property of the PictureBox), the new bitmap had a different (=default) resolution setting. By changing the resolution setting to match the one from the source bitmap (the original screendump), the problem went away!

Resize transparent image with Magick.NET

I got some weird issues when resizing an image with transparency in Magick.NET. I am using Q16-AnyCPU.
I am resizing a 100px image to 400px.
MagickImage image = new MagickImage("test.png");
image.Resize(400, 400);
image.Write("test_resized.png");
I have tried many combinations of image.FilterType and image.Interpolate without any good results.
Only when I use image.AdaptiveResize(400, 400);, it looks somewhat better, but not as expected. The final image I want to resize is much bigger and AdaptiveResize is very slow.
When I disable Alpha via image.Alpha(AlphaOption.Off); I looks quice nice, but I want to keep the alpha.
Source image (the white area is transparent):
What I get:
What I want:

I had to set VirtuaPixelMethod, thanks for the hint:
MagickImage image = new MagickImage("test.png");
image.VirtualPixelMethod = VirtualPixelMethod.Transparent;
image.Resize(400, 400);
image.Write("test_resized.png");

How to show a YCbCr image using Emgu in C#?

I got a bitmap as a source;
I created a Emgu image with Image<Bgr,Byte> img = new Image<Bgr,Byte>(bmp);
I converted it to a YCbCr image using Image<Ycc,Byte> YCB = img.Convert<Ycc,Byte>();
I dragged a imagebox from the toolbox and assigned it with YCB -----> imagebox1.Image=YCB;
but the result shows the image in RGB format just like source bitmap
I don't understand where went wrong
Could someone give me some clues?

Have you made any alterations to YCB? If you simply display it then it will look identical to the original.
If you right click on your imagebox when running your program and select property it will tell you the type of image and show you the data held within the YCB image this should be different from your original. Alternatively just show 1 channel of your image matrix so for your BGR show the blue colour this will obviously be displayed as a single colour grayscale image. Now for the YCB show the Luma channel again this will be displayed as a single colour grayscale image. You will notice a slight change between them as the luma represents the luminance of all 3 colour spectrums.
CvInvoke.cvShowImage("Blue", img [0]);
CvInvoke.cvShowImage("Luma", YCB[0]);
If you want to see a greater difference multiply the Luma by 2 and you have a completely different image.
YCB[0] *= 2;
CvInvoke.cvShowImage("Luma Change", YCB);
The CvInvoke.cvShowImage() method is a great tool for debugging your code and seeing what your code is doing to images step by step.
For the benefits of others Ycc is YCbCr colour space: http://en.wikipedia.org/wiki/YCbCr
Cheers,
Chris

Images Scaling Down in draw in C#

Alright guys last little bit of this project I'll ask for help on I promise.
So I go to load the images, works fine however I notice upon loading that the dimensions of the image have been scaled down in the y to 300 (all are a constant value of 433) and up or down from their original width to 600.
I'm using the following method to load them
foreach (string file in Directory.EnumerateFiles(imagePath, "*.JPG"))
{
Image contents = Image.FromFile(file);
treesImage[count] = contents;
count++;
}
and this is the resulting image when I have it loaded.
http://i.stack.imgur.com/Q40kK.png
As you can see the image below the red rectangle is quite small
Any help would be appreciated. If you require any more information please post below and I'll make sure to edit the original question with the relevant information as soon as humanly possible.
EDIT: I am using a simple windows form application and not another graphical framework for my own reasons.
Thanks in advance :)

I'll assume you are using a PictureBox control to display the image.
When someone chooses a tree from your map, you obviously set the PictureBox Image property to the image object referenced by the index in the array. Use the Image object to set the ClientSize of the PictureBox control.
...
Image img = treesImage[idx];
MyPictureBox.SizeMode = PictureBoxSizeMode.Normal;
MyPictureBox.ClientSize = new Size(img.Width,img.Height);
MyPictureBox.Image = img;
...
Alternately you can define one size for your PictureBox and force all the images to be scaled to that size by setting the control SizeMode property to StretchImage declaratively.
I would recommend that you create a simple class (MyImageInfo for example) that would store the Path, Width, and Height of the images found in your first function into a list and then just as before when a user clicks to view an image you set the width and height of the PictureBox and then call the LoadAsync(path) method to get the image. then you aren't storing all images in memory at once, just as you need them since it doesn't look like this requires a lot of quick jumping from image to image.

C#: Retain size despite different resolution using Graphics.DrawImage

I am trying to draw two images side-by-side using the C# Drawing namespace.
Here is a very simple example that assumes we have two images of the same height:
Image[] oldImages = GetOldImages();
var newImage = new Bitmap(oldImages[0].Width + oldImages[1].Width, 800);
using (var newImageGraphics = Graphics.FromImage(newImage))
{
newImageGraphics.DrawImage(oldImages[0], 0, 0);
newImageGraphics.DrawImage(oldImages[1], oldImage[0].Width, 0);
newImageGraphics.Save();
}
This works OK if the resolution of the two old images are the same.
However, if the resolutions are different then the image is resized, causing problems. For example, if the first image has a different resolution, then the second image will be positioned incorrectly.
Does anyone know how I can fix this problem easily? Ideally I want the original image's height and width to remain the same when they are drawn on to the new image.

Try this trick:
Bitmap picture_1 = new Bitmap(picture_1_path);
Graphics graphics = Graphics.FromImage(picture_1);
Bitmap picture_2 = new Bitmap(picture_2_path);
picture_2.SetResolution(graphics.DpiX, graphics.DpiY);
//Then do with pictures anything

Basically you'll need to resize the second image before adding to the new image.
Though as you say you want to retain the original height and width you'll need to change the canvas size of the second image. This increases the size of the image by adding empty space around the actual image. If the second image is larger than the first you'll need to do this to the first image instead.