C# Archives - Efundies.com

Image vs Bitmap in C#

December 29, 2015 Jason Bauer One comment

A lot of people get confused about when to use the Bitmap class and when to use the Image class in C#. All of our examples on this site tend to use the Bitmap class because it is, for the most part, the easier class to use when getting started. The big difference between the Image class and the Bitmap […]

Scale an Image in C# Preserving Aspect Ratio

December 29, 2015 Jason Bauer 3 comments

If you need to change the size of an Image without changing the ratio of X to Y then this function should do what you want. The input parameters maxWidth and maxHeight define the largest values that you want to get back out of the image after it has been scaled.

public static Bitmap ScaleImage(Bitmap bmp, int maxWidth, int maxHeight)
{
    var ratioX = (double)maxWidth / bmp.Width;
    var ratioY = (double)maxHeight / bmp.Height;
    var ratio = Math.Min(ratioX, ratioY);

    var newWidth = (int)(bmp.Width * ratio);
    var newHeight = (int)(bmp.Height * ratio);

    var newImage = new Bitmap(newWidth, newHeight);

    using (var graphics = Graphics.FromImage(newImage))
        graphics.DrawImage(bmp, 0, 0, newWidth, newHeight);

    return newImage;
}

public static Bitmap ScaleImage(Bitmap bmp, int maxWidth, int maxHeight)

{

var ratioX = (double)maxWidth / bmp.Width;

var ratioY = (double)maxHeight / bmp.Height;

var ratio = Math.Min(ratioX, ratioY);

var newWidth = (int)(bmp.Width * ratio);

var newHeight = (int)(bmp.Height * ratio);

var newImage = new Bitmap(newWidth, newHeight);

using (var graphics = Graphics.FromImage(newImage))

graphics.DrawImage(bmp, 0, 0, newWidth, newHeight);

return newImage;

}

Results of Scaling an Image Here is a […]

Adjust the Contrast of an Image in C#

December 29, 2015 Jason Bauer Leave a comment

Adjusting the contrast of an image in C# is an easy operation because it can be done on a single pixel at a time. We only need to know 2 formulas to calculate a new pixel color based on an old pixel color, and they’re very easy to implement. contrast = ((100.0 + T) / 100.0)2 newRed = ( ( ( (oldRed […]

Lighten an Image in C#

December 29, 2015 Jason Bauer Leave a comment

In order to lighten an image in C# you need to look at each pixel one at a time and increase it’s reg, green, and blue values. There are a few ways to do this. The easiest way is just just increment the reg, green, and blue by a fixed percentage, and limit their maximum value to 255. The hard […]

Darken an Image in C#

December 29, 2015 Jason Bauer Leave a comment

In order to darken an image in C# you need to look at each pixel one at a time and decrease it’s reg, green, and blue values. There are a few ways to do this. The easiest way is just just decrement the reg, green, and blue by a fixed percentage, and limit their minimum value to 0. The hard […]

Convert an Image to Gray Scale in C#

December 27, 2015 Jason Bauer Leave a comment

Sometimes you need to take a color image and remove all of the color from it leaving just shades of gray. There are 3 common ways of performing this calculation, each yielding slightly different results. The Lightness method The Average method The Luminosity method They are all very easy to implement in C#. In this example we’ll use the Luminosity […]

Replace A Color in an Image with C#

December 27, 2015 Jason Bauer 3 comments

Sometimes you need to replace one color in an image with another color. In C# we do this by first opening the image up from file and loading it into a Bitmap object. Once we have it in a Bitmap we can iterate over the x and y values looking at 1 pixel at a time. Each time we look […]

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