Develop Reference

Crop white space around black image based on color

I using Imaemagick and c# and wondering:
Is it possible to crop image to border without exactly sizes?
From first to second?
First image
Second

To remove the white space around the sudoku square you can loop over the pixels. Since the image is black and white it makes it a lot easier because we can check when any of the R, G or B values drop below a certain white threshold and become black.
In this example, I'm just using an arbitrary 200 value to check.
I'm walking in from the top left and bottom right corners. This will only work if your image is always a perfect square. but you can easily adjust this code to check coordinates more accurately to meet your purposes.
using (var image = new Bitmap(Image.FromFile("firstImage.jpg")))
{
int topX = 0, topY = 0;
int bottomX = image.Width - 1, bottomY = image.Height - 1;
var color = image.GetPixel(topX, topY);
while(color.R > 200)
color = image.GetPixel(++topX, ++topY);
color = image.GetPixel(bottomX, bottomY);
while(color.R > 200)
color = image.GetPixel(--bottomX, --bottomY);
Bitmap croppedImage = new Bitmap(image);
Rectangle cropRect = new Rectangle(topX, topY, bottomX - topX + 1, bottomY - topY + 1);
croppedImage = croppedImage.Clone(cropRect, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
croppedImage.Save("firstImageNoBorder.jpg");
}
Original:
Cropped:

c# drawing text using custom pixels

I'm wondering if that's possible:
I got a c# application with something like a display consisting of about 11000 circles drawn on the Form.
What I want to achieve is to be able to draw text on that display, but not using the "real" pixels, but using the circles (rectangles) drawn on the form as pixels.
Edit 1:
When drawing text in c#, you would i.e. use something like Graphics.DrawString(...), giving the method a rectangle (so coordinates) in which the text should be drawn in. That text then is drawn in that rectangle using the screen pixels. What I want to do is draw text as well but not using the screen pixels but my custom pixels of which my display consists.
Edit 2
Method used to draw the circles on the Form; Circles is a list consisting of Circle objects, where circleRectangle returns the coordinates in which the circle should be drawn and Filled tells the method if the circle should be filled or not.
public void DrawCircles(Graphics g)
{
graphics = g;
graphics.SmoothingMode =System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
Pen pen = new Pen(Color.Black, penthickness);
SolidBrush brush = new SolidBrush(Color.White);
for (int j = 0; j < Circles.Count;j++ )
{
graphics.DrawEllipse(pen, Circles[j].CircleRectangle);
if (Circles[j].Filled)
brush.Color = fillColor;
else
brush.Color = Color.White;
graphics.FillEllipse(brush, Circles[j].CircleRectangle);
}
}
Is this possible and if yes, how would I do that?

You could write on an invisible BitMap with the DrawText method and then scan the bitmap's pixels and turn the corresponding circles on.
Did that last week with the cells of DataGridView. Real easy.
Here is some code:
public void drawText(string text, Font drawFont)
{
Bitmap bmp = new Bitmap(canvasWidth, canvasHeight);
Graphics G = Graphics.FromImage(bmp);
SolidBrush brush = new SolidBrush(paintColor);
Point point = new Point( yourOriginX, yourOriginY );
G.DrawString(text, drawFont, brush, point);
for (int x = 0; x < canvasWidth; x++)
for (int y = 0; y < canvasHeight; y++)
{
Color pix = bmp.GetPixel(x, y);
setCell(x, y, pix); //< -- set your custom pixels here!
}
bmp.Dispose();
brush.Dispose();
G.Dispose();
}
Edit: You would use your dimensions and your origin for the DrawString, of course

The best way to change color of GRAY image C#

I have a dilemma. At the first glance my task is simple enough, but I definitely have some troubles with it. I have an image. Gray image. And I need to get colored image. Pictures show it best.
I know two ways to do this:
1) changing tint,
2) changing hue (rotating color matrix)
Tint changes common color and also black. So I believe that this way is not suitable in my case.
Hue changing requires base image to be already colored, but all images are grey (with gradient) initially. But it works fine as it needed.
So I am a little confused about the way of solving this task.
May be there are some other ways to do what I need to do?
I am greatly appreciate your help, guys!
Thank you in advance!
↑This is a base image↑
↑Similar is needed to be achieved↑
↑Tinted image↑

I have written some code to pass the grayscale component as yellow color (shared between the R and G components) i have got close enough results, all you need to do is to play with the R and G components ratios to get the degree of the yellow color you need. also you need to search more on how to handle the shadow at the bottom of the object.
// Load image
Bitmap bm = new Bitmap("D:\\a.png");
for (int i = 0; i < bm.Width; i++)
{
for (int j = 0; j < bm.Height; j++)
{
// Handles transparent pixles
if (bm.GetPixel(i, j).R == 0 & bm.GetPixel(i, j).G == 0 & bm.GetPixel(i, j).B == 0 & bm.GetPixel(i, j).A == 0) bm.SetPixel(i, j, Color.Transparent);
// Passes the grey component of the grescale image to R and G compenents and changes pixle color
else bm.SetPixel(i, j, Color.FromArgb(bm.GetPixel(i, j).R, bm.GetPixel(i, j).R, 0));
}
}
// Save image
bm.Save("D:\\b.png");
Here is the result i got from the posted image

I wrote these two methods that do the job. You can set any color you want your image to be blended with.
private void ApplyColor(Bitmap bm, Color userColor)
{
if (bm==null)
return;
// pixels loop
for (int i = 0; i < bm.Width; i++)
{
for (int j = 0; j < bm.Height; j++)
{
// get current pixel
Color curPix = bm.GetPixel(i, j);
Color curPixColor = Color.FromArgb(curPix.A, curPix.R, curPix.G, curPix.B);
// get result color by blending
Color resultColor = Blend(curPixColor, userColor, ColorMixFactor);
// set pixel color
bm.SetPixel(i, j, resultColor);
}
}
}
public static Color Blend(Color srcColor, Color dstColor, double amount)
{
// restrict black (dark) color from being affected by the blending
var br = srcColor.GetBrightness();
if (br < BrightnessToAvoid)
return srcColor;
// get all 4 color channels
var r = (byte) ((srcColor.R*amount) + dstColor.R*(1 - amount));
var g = (byte) ((srcColor.G*amount) + dstColor.G*(1 - amount));
var b = (byte) ((srcColor.B*amount) + dstColor.B*(1 - amount));
var a = srcColor.A;
// get blended color
return Color.FromArgb(a, r, g, b);
}

Fill the holes in emgu cv

How can I fill the holes in binary image in emgu cv?
In Aforge.net it's easy, use Fillholes class.

Thought the question is a little bit old, I'd like to contribute an alternative solution to the problem.
You can obtain the same result as Chris' without memory problem if you use the following:
private Image<Gray,byte> FillHoles(Image<Gray,byte> image)
{
var resultImage = image.CopyBlank();
Gray gray = new Gray(255);
using (var mem = new MemStorage())
{
for (var contour = image.FindContours(
CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE,
RETR_TYPE.CV_RETR_CCOMP,
mem); contour!= null; contour = contour.HNext)
{
resultImage.Draw(contour, gray, -1);
}
}
return resultImage;
}
The good thing about the method above is that you can selectively fill holes that meets your criteria. For example, you may want to fill holes whose pixel count (count of black pixels inside the blob) is below 50, etc.
private Image<Gray,byte> FillHoles(Image<Gray,byte> image, int minArea, int maxArea)
{
var resultImage = image.CopyBlank();
Gray gray = new Gray(255);
using (var mem = new MemStorage())
{
for (var contour = image.FindContours(
CHAIN_APPROX_METHOD.CV_CHAIN_APPROX_SIMPLE,
RETR_TYPE.CV_RETR_CCOMP,
mem); contour!= null; contour = contour.HNext)
{
if ( (contour.Area < maxArea) && (contour.Area > minArea) )
resultImage.Draw(contour, gray, -1);
}
}
return resultImage;
}

Yes there is a method but it's a bit messy as its based on cvFloodFill operation. Now all this algorithm is designed to do is fill an area with a colour until it reaches an edge similar to a region growing algorithm. To use this effectively you need to use a little inventive coding but I warn you this code is only to get you started it may require re-factoring to speed things up . As it stands the loop goes through each of your pixels that are less then 255 applies cvFloodFill checks what size the area is and then if it is under a certain area fill it in.
It is important to note that a copy of the image is made of the original image to be supplied to the cvFloodFill operation as a pointer is used. If the direct image is supplied then you will end up with a white image.
OpenFileDialog OpenFile = new OpenFileDialog();
if (OpenFileDialog.ShowDialog() == DialogResult.OK)
{
Image<Bgr, byte> image = new Image<Bgr, byte>(OpenFile.FileName);
for (int i = 0; i < image.Width; i++)
{
for (int j = 0; j < image.Height; j++)
{
if (image.Data[j, i, 0] != 255)
{
Image<Bgr, byte> image_copy = image.Copy();
Image<Gray, byte> mask = new Image<Gray, byte>(image.Width + 2, image.Height + 2);
MCvConnectedComp comp = new MCvConnectedComp();
Point point1 = new Point(i, j);
//CvInvoke.cvFloodFill(
CvInvoke.cvFloodFill(image_copy.Ptr, point1, new MCvScalar(255, 255, 255, 255),
new MCvScalar(0, 0, 0),
new MCvScalar(0, 0, 0), out comp,
Emgu.CV.CvEnum.CONNECTIVITY.EIGHT_CONNECTED,
Emgu.CV.CvEnum.FLOODFILL_FLAG.DEFAULT, mask.Ptr);
if (comp.area < 10000)
{
image = image_copy.Copy();
}
}
}
}
}
The "new MCvScalar(0, 0, 0), new MCvScalar(0, 0, 0)," are not really important in this case as you are only filling in results of a binary image. YOu could play around with other settings to see what results you can achieve. "if (comp.area < 10000)" is the key constant to change is you want to change what size hole the method will fill.
These are the results that you can expect:
Original
Results
The problem with this method is it's extremely memory intensive and it managed to eat up 6GB of ram on a 200x200 image and when I tried 200x300 it ate all 8GB of my RAM and brought everything to a crashing halt. Unless a majority of your image is white and you want to fill in tiny gaps or you can minimise where you apply the method I would avoid it. I would suggest writing you own class to examine each pixel that is not 255 and add the number of pixels surrounding it. You can then record the position of each pixel that was not 255 (in a simple list) and if your count was bellow a threshold set these positions to 255 in your images (by iterating though the list).
I would stick with the Aforge FillHoles class if you do not wish to write your own as it is designed for this purpose.
Cheers
Chris

you can use FillConvexPoly
image.FillConvexPoly(externalContours.ToArray(), new Gray(255));

How do I superimpose one bitmap image on another in GDI+?

Using GDI+ I've made a heatmap bmp and I'd like to superimpose it on top of my bmp map. I've saved the two bmps to disk, and they look good, I just need a way to put them together. Is there any way to do this, perhaps using the Graphics object? How is transparency/alpa involved?
I'm very new to GDI programming so please be as specific as possible.
OK - here's an answer. At some point I need to learn how GDI+ works...
I couldn't get around the transarency issues, but this works. It just copies the non-white pixels from the overlay to the map:
for (int x = 0; x < map.Width; x++)
for (int y = 0; y < map.Height; y++) {
Color c = overlay.GetPixel(x, y);
if ((c.A != 255) || (c.B != 255) || (c.G != 255) || (c.R != 255))
map.SetPixel(x, y, c);

This should do the job...
At the moment the Image you want to superimpose onto the main image will be located in the top left corner of the main Image, hence the new Point(0,0). However you could change this to locate the image anywhere you want.
void SuperimposeImage()
{
//load both images
Image mainImage = Bitmap.FromFile("PathOfImageGoesHere");
Image imposeImage = Bitmap.FromFile("PathOfImageGoesHere");
//create graphics from main image
using (Graphics g = Graphics.FromImage(mainImage))
{
//draw other image on top of main Image
g.DrawImage(imposeImage, new Point(0, 0));
//save new image
mainImage.Save("OutputFileName");
}
}