Develop Reference

C# white or black unwanted pixels appear in the image

I am new to C#, I am using Visual Studo 2010, I have an image that needs to be displayed on a picturebox.
I tried many different methods. All the methods results in some unwanted pixels to appear along with image.
I have tried
picturebox.Image = Image.FromFile("bird.png");
result->
the image is displayed but with the stray white/black pixels at random places.
I also tried creating a bitmap of same size and drawing the image onto the bitmap and then assigning the bitmap to the picture box.Image. Still those unwanted pixels are visible.
I have tried clearing the picture box image (filling it with white or transparent) and then assigning the image, still same error occurs.
PS: this doesn't happen for all the images only certain images show this behaviour.
any help would be great
Code:
Image org = Bitmap.FromFile("bird.png");
Bitmap final = new Bitmap(org.Width,org.Height);
using (Graphics g = Graphics.FromImage(final))
{
g.DrawImage(org,0,0,GraphicsUnit.Pixel);
}
picturebox.Image = final;
if i use final.save("picture.png"). The "picuture.png" does not have that wrong pixels, it happens only when i use picture box to display it.
Please find the images attached defect orginal
PS: its not because of different fileformat (orginal and defect)

It was an TransperancyKey issue resolved by setting it to Default.

Trying to add transparent text with TextRenderer.DrawText to a bitmap image

I'm actually trying to add some text to an image in C# with
System.Windows.Forms.TextRenderer.DrawText(Graphics, string, Rectangle, Color, TextFormaFlags)
I prepare my image (which is a png) by loading it in memory, with something similar to
Image image = ImageCache.Get(...);
bitmap = new Bitmap(image);
graphic = Graphics.FromImage(bitmap);
I then draw my text with the above command. The problem is that whatever I use for the color, even something like
System.Drawing.Color.FromArgb(0,255,255,255)
the transparency is not drawn. I tried many settings for
graphics.TextRenderingHint
and different combinations of fonts, transparency level, etc. Is there something I don't understand here? Any hint is appreciated.
Thank you.

As mentionned in the comments : if you try to draw transparent text with
System.Windows.Forms.TextRenderer.DrawText
because you look for the advantages brought by GDI in C#, you just can't. Use
System.Drawing.Graphics.DrawString
instead, even if the result for the word-wrapping is slightly inferior with GDI+.

Save transparent GIFs in GDI+ or WPF

I am trying to save a GIF with transparency in GDI+, but it seems to reuse the first color in the color table - is this a bug with GDI?
Even if I manually set the colour and resave a gif to a gif, I can't ever get it to output a transparent gif to file:
Bitmap b = new Bitmap("c:\\temp\\source.gif");
Bitmap canvas = new Bitmap(b.Width, b.Height);
Graphics g = Graphics.FromImage(canvas);
g.Clear(Color.Transparent);
// Draw image
g.DrawImage(b, 0, 0);
canvas.MakeTransparent(Color.Black);
canvas.Save("c:\\temp\\output.gif", System.Drawing.Imaging.ImageFormat.Gif);
In the output image black is never set as the transparency colour.
Alternatively is there a way to do this in WPF?

I suggest you take a look at this Image processing Library ImageMagick http://www.imagemagick.org/
Then use this command to convert the saved gif to a gif with transparent background
convert orig.gif -transparent black transp.gif
This might not produce perfect results but worth a try.You might also want to take a look at ImageMagick's .NET Wrapper https://magick.codeplex.com/ ,if you dont want to do this by running a console command.

C# Winform Image zoom with pixelate

I'm making simple image editor by C# winform.
I'm trouble with make zoom function. in other similar questions, many people simply suggest that 'change the size' such like..
Bitmap newImg = new Bitmap(oldImg, newWidth, newHeight);
But In this way, the picture become blured(is it caused by antialiasing? I don't know well...) I need pixelated zoom Image. Like any other image editor such as Photoshop or paint.net...
I tried also put pixelate function to make mosaic image. result was good but it was too slow!
please help me. How can I make pixelate zoom?

Check out Image resizing in .Net with Antialiasing, this should get you started (I'm not sure but setting SmoothingMode = SmoothingMode.None means no anitaliasing).

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.