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Trimming Bitmap Causes Cutting of Text at Bottom

I'm using the following code to remove whitespace around an image.
static Bitmap TrimBitmap(Bitmap source)
{
Rectangle srcRect = default(Rectangle);
BitmapData data = null;
try
{
data = source.LockBits(new Rectangle(0, 0, source.Width, source.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
byte[] buffer = new byte[data.Height * data.Stride];
Marshal.Copy(data.Scan0, buffer, 0, buffer.Length);
int xMin = int.MaxValue,
xMax = int.MinValue,
yMin = int.MaxValue,
yMax = int.MinValue;
bool foundPixel = false;
// Find xMin
for (int x = 0; x < data.Width; x++)
{
bool stop = false;
for (int y = 0; y < data.Height; y++)
{
byte alpha = buffer[y * data.Stride + 4 * x + 3];
if (alpha != 0)
{
xMin = x;
stop = true;
foundPixel = true;
break;
}
}
if (stop)
break;
}
// Image is empty...
if (!foundPixel)
return null;
// Find yMin
for (int y = 0; y < data.Height; y++)
{
bool stop = false;
for (int x = xMin; x < data.Width; x++)
{
byte alpha = buffer[y * data.Stride + 4 * x + 3];
if (alpha != 0)
{
yMin = y;
stop = true;
break;
}
}
if (stop)
break;
}
// Find xMax
for (int x = data.Width - 1; x >= xMin; x--)
{
bool stop = false;
for (int y = yMin; y < data.Height; y++)
{
byte alpha = buffer[y * data.Stride + 4 * x + 3];
if (alpha != 0)
{
xMax = x;
stop = true;
break;
}
}
if (stop)
break;
}
// Find yMax
for (int y = data.Height - 1; y >= yMin; y--)
{
bool stop = false;
for (int x = xMin; x <= xMax; x++)
{
byte alpha = buffer[y * data.Stride + 4 * x + 3];
if (alpha != 0)
{
yMax = y;
stop = true;
break;
}
}
if (stop)
break;
}
srcRect = Rectangle.FromLTRB(xMin, yMin, xMax , yMax);
}
finally
{
if (data != null)
source.UnlockBits(data);
}
Bitmap dest = new Bitmap(srcRect.Width, srcRect.Height);
Rectangle destRect = new Rectangle(0, 0, srcRect.Width, srcRect.Height);
using (Graphics graphics = Graphics.FromImage(dest))
{
graphics.DrawImage(source, destRect, srcRect, GraphicsUnit.Pixel);
}
return dest;
}
I'm trying to trim a Bitmap with Text Drawn on it.The Proper Image should look like this after trimming
But after trimming i get the following result ..the bottom portion clipped off
What i'm i doing wrong? Please advice..

This is actually a problem with Rectangle.FromLTRB !
Looking closer at the images you will find that you have actually lost only one row of pixels. (The strong magnification had me fooled for a while..)
The algorithm to determine the Height (and Width) of the rectangle is basically right, but off by one.
If you use this
srcRect = Rectangle.FromLTRB(xMin, yMin, xMax + 1 , yMax + 1);
or this:
srcRect = new Rectangle(xMin, yMin, xMax - xMin + 1 , yMax - yMin + 1);
it should work.
You can test with pen and paper: Say: 1st pixel row with a color = 4, first from bottom on a 10 pixel square: 8, that makes 5 not 4 net data: 4,5,6,7,8.
Do note that this issue is inherent in FromLTRB:
Rectangle myRectangle = Rectangle.FromLTRB(0, 0, 10, 10);
..results in a Rectangle with Height=10 even though 0..10 should cover 11 pixels rows! So the Right-Bottom coordinate is actually excluded from the result!!
I think the whole issue with rectangles being off by one stems from legacy ways to use a Pen with its alignment. When using the same rectangles to fill with a Brush all works as expected.

Looping through pixels excluding an area

I have the following code for looping pixels in an image:
Bitmap myBitmap = new Bitmap(pictureBox1.Image);
for (x = 0; x < pictureBox1.Image.Width; x += 1)
{
for (y = 0; y < pictureBox1.Image.Height; y += 1)
{
Color pixelColor = myBitmap.GetPixel(x, y);
aws = pixelColor.GetBrightness();
}
}
The above works. What if i want to exclude an area of the image. The area is an area selected by the user,for example:
from x=200&y=30 to x=250&y=30
from x=200&y=35 to x=250&y=35
from x=200&y=40 to x=250&y=40
from x=200&y=45 to x=250&y=45
How i loop all pixels except the one i wrote above?
Thank you!

I think you can do something like the following
Rectangle rectToExclude = new Rectangle(200, 30, 250, 30);//rectangle to be excluded
Bitmap myBitmap = new Bitmap(pictureBox1.Image);
for (x = 0; x < pictureBox1.Image.Width; x += 1)
{
for (y = 0; y < pictureBox1.Image.Height; y += 1)
{
if (rectToExclude.Contains(x, y)) continue; // if in the exclude rect then continue without doing any effects
Color pixelColor = myBitmap.GetPixel(x, y);
aws = pixelColor.GetBrightness();
}
}

Maybe write a function to test x and y like this:
public static bool IsInArea(int testx, int testy, int x1, int y1, int x2, int y2)
{
if (testx > x1 && testx < x2 && testy > y1 && testy < y2)
{
return true;
}
else
{
return false;
}
}
and then use it like this:
BitmapData bmd = myBitmap.LockBits(new Rectangle(0, 0, myBitmap.Width, myBitmap.Height),
System.Drawing.Imaging.ImageLockMode.ReadWrite,
myBitmap.PixelFormat);
int PixelSize = 4;
unsafe
{
for (int y = 0; y < bmd.Height; y++)
{
byte* row = (byte*)bmd.Scan0 + (y * bmd.Stride);
for (int x = 0; x < bmd.Width; x++)
{
if (!IsInArea(x, y, 200, 30, 250, 30))
{
int b = row[x * PixelSize]; //Blue
int g = row[x * PixelSize + 1]; //Green
int r = row[x * PixelSize + 2]; //Red
int a = row[x * PixelSize + 3]; //Alpha
Color c = Color.FromArgb(a, r, g, b);
float brightness = c.GetBrightness();
}
}
}
}
myBitmap.UnlockBits(bmd);

Crop image white space in C#

I have the request that crop image white space in C#, and I search some methods from the forum, but it could not satisfy my request.
There is the original image,
This is the result I expect,
Any help are appreciate.

You can try to get first image data(There is an image), and draw the data into a new image. Try this method. Hope it can help you.
private static Bitmap ImageTrim(Bitmap img)
{
//get image data
BitmapData bd= img.LockBits(new Rectangle(Point.Empty, img.Size),
ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
int[] rgbValues = new int[img.Height * img.Width];
Marshal.Copy(bd.Scan0, rgbValues, 0, rgbValues.Length);
img.UnlockBits(bd);
#region determine bounds
int left = bd.Width;
int top = bd.Height;
int right = 0;
int bottom = 0;
//determine top
for (int i = 0; i < rgbValues.Length; i++)
{
int color = rgbValues[i] & 0xffffff;
if (color != 0xffffff)
{
int r = i / bd.Width;
int c = i % bd.Width;
if (left > c)
{
left = c;
}
if (right < c)
{
right = c;
}
bottom = r;
top = r;
break;
}
}
//determine bottom
for (int i = rgbValues.Length - 1; i >= 0; i--)
{
int color = rgbValues[i] & 0xffffff;
if (color != 0xffffff)
{
int r = i / bd.Width;
int c = i % bd.Width;
if (left > c)
{
left = c;
}
if (right < c)
{
right = c;
}
bottom = r;
break;
}
}
if (bottom > top)
{
for (int r = top + 1; r < bottom; r++)
{
//determine left
for (int c = 0; c < left; c++)
{
int color = rgbValues[r * bd.Width + c] & 0xffffff;
if (color != 0xffffff)
{
if (left > c)
{
left = c;
break;
}
}
}
//determine right
for (int c = bd.Width - 1; c > right; c--)
{
int color = rgbValues[r * bd.Width + c] & 0xffffff;
if (color != 0xffffff)
{
if (right < c)
{
right = c;
break;
}
}
}
}
}
int width = right - left + 1;
int height = bottom - top + 1;
#endregion
//copy image data
int[] imgData = new int[width * height];
for (int r = top; r <= bottom; r++)
{
Array.Copy(rgbValues, r * bd.Width + left, imgData, (r - top) * width, width);
}
//create new image
Bitmap newImage = new Bitmap(width, height, PixelFormat.Format32bppArgb);
BitmapData nbd
= newImage.LockBits(new Rectangle(0, 0, width, height),
ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
Marshal.Copy(imgData, 0, nbd.Scan0, imgData.Length);
newImage.UnlockBits(nbd);
return newImage;
}

If your image only has 2 colors (white and black), you can iterate through your image and find the top left pixel set and the bottom right pixel set, then you can crop it:
(pseudo code, depends on what you use to get your image pixels)
int minX = int.MaxValue, maxX = 0, minY = int.MaxValue, maxY = 0;
for (x = 0; x < image.Width, x++)
{
for (y = 0; y < image.Height; y++)
{
if (image[x, y] == 1)
{
if (x < minX) minX = x;
else if (x > maxX) maxX = x;
if (y < minY) minY = y;
else if (y > maxY) maxY = y;
}
}
}
then you'll have the coordinates that will let you crop the image
I'm sure this could be optimized but that's the general idea

Drawing a border on an image

I'm currently trying to make a mask generator to generate polygons for images. Here's my code.
Bitmap bmp = new Bitmap(file);
int w = bmp.Width;
int h = bmp.Height;
List<Point> vertices = new List<Point>();
for (int y=0; y<h; y++)
{
bool rowbegin = false;
for (int x=0; x<w; x++)
{
Color c = bmp.GetPixel(x, y);
if (!rowbegin)
{
// Check for a non alpha color
if (c.A != Color.Transparent.A)
{
rowbegin = true;
// This is the first point in the row
vertices.Add(new Point(x, y));
}
} else {
// Check for an alpha color
if (c.A == Color.Transparent.A)
{
// The previous pixel is the last point in the row
vertices.Add(new Point(x-1, y));
rowbegin = false;
}
}
}
}
// Convert to an array of points
Point[] polygon = vertices.ToArray();
Graphics g = Graphics.FromImage(bmp);
g.DrawPolygon(Pens.LawnGreen, polygon);
g.Dispose();
But I'm getting wrong output.
The required.
What I want is also the gaps between the characters to be empty. Also why DrawPolygon is filling it?
Thanks.

Do you trying something like this:i hope my code help you:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
Bitmap bmp = new Bitmap(#"C:\Users\Ali\Desktop\1.png");
int w = bmp.Width;
int h = bmp.Height;
Lst_Data lastpointcolor = new Lst_Data() ;
for (int y = 0; y < h; y++)
{
for (int x = 0; x < w; x++)
{
Color c = bmp.GetPixel(x, y);
if (c.A != Color.Transparent.A)
{
if (lastpointcolor.color.A == Color.Transparent.A)
{
bmp.SetPixel(lastpointcolor.point.X, lastpointcolor.point.Y, Color.Red);
}
}
lastpointcolor = new Lst_Data() { point = new Point(x, y), color = bmp.GetPixel(x, y) };
}
}
for (int y = h-1; y > 0; y--)
{
for (int x = w-1; x > 0; x--)
{
Color c = bmp.GetPixel(x, y);
if (c.A != Color.Transparent.A)
{
if (lastpointcolor.color.A == Color.Transparent.A)
{
bmp.SetPixel(lastpointcolor.point.X, lastpointcolor.point.Y, Color.Red);
}
}
lastpointcolor = new Lst_Data() { point = new Point(x, y), color = bmp.GetPixel(x, y) };
}
}
pictureBox1.Image = bmp;
}
}
public struct Lst_Data
{
public Point point;
public Color color;
}
}
Edited:
And Another idea i have for you:D
Make a mask for original image with the same size and do this:
Bitmap orginal = new Bitmap(#"C:\Users\Ali\Desktop\orginal.png");
Bitmap mask = new Bitmap(#"C:\Users\Ali\Desktop\mask.png");
for (int i = 0; i < orginal.Width; i++)
{
for (int j = 0; j < orginal.Height; j++)
{
if (orginal.GetPixel(i, j).A == Color.Transparent.A)
{
mask.SetPixel(i, j, Color.Transparent);
}
}
}
Bitmap bitmap = new Bitmap(mask, mask.Height, mask.Height);
using (Graphics g = Graphics.FromImage(bitmap))
{
g.DrawImage(mask, 0, 0);
g.DrawImage(orginal,0,0);
}
pictureBox1.Image = bitmap;
Result:

Getting cell co ordinates on Honeycomb pattern

I have to draw a honeycomb pattern and recognize each cell(row,column) on mousemove.
this is how i am generating the graph.
protected override void GenerateGridBitmap()
{
if (_circleGrid != null)
{
_circleGrid.Dispose();
_circleGrid = null;
}
Bitmap _texture = new Bitmap(circleSize, circleSize);
using (Graphics g = Graphics.FromImage(_texture))
{
g.SmoothingMode = SmoothingMode.HighQuality;
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.PixelOffsetMode = PixelOffsetMode.HighQuality;
Rectangle r = new Rectangle(0, 0, circleSize, circleSize);
g.DrawEllipse(Pens.Black, r);
}
Bitmap rowBlock = new Bitmap(CanvasSize.Width - (circleSize/ 2), circleSize);
using (Brush b = new TextureBrush(_texture))
{
using (Graphics g = Graphics.FromImage(rowBlock))
{
g.CompositingQuality = CompositingQuality.HighQuality;
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.SmoothingMode = SmoothingMode.HighQuality;
g.FillRectangle(b, new Rectangle(new Point(0, 0), rowBlock.Size));
}
}
//rowBlock.Save("rowblock.bmp");
_circleGrid = new Bitmap(CanvasSize.Width, CanvasSize.Height);
using (Graphics g = Graphics.FromImage(_circleGrid))
{
g.CompositingQuality = CompositingQuality.HighQuality;
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.SmoothingMode = SmoothingMode.HighQuality;
int x, y;
for (int i = 0; i < rows; i++)
{
x = 0;
if (i % 2 != 0)
x = (circleSize/ 2);
y = (i * circleSize);
if (i != 0)
{
y -= (VERTICAL_PIXEL_OFFSET * i);
}
g.DrawImage(rowBlock, x, y);
//g.DrawImage(DrawCodedCrystal(i,rowBlock), x, y);
Console.WriteLine(i);
}
}
_circleGrid.Save("grid.bmp");
Console.WriteLine(_circleGrid.Size);
_texture.Dispose();
_texture = null;
rowBlock.Dispose();
rowBlock = null;
}
and this what i am doing to get the coordinates of the graph. but the problem is i am able to get the column perfectly. but for the row i think there is a small difference in calculation. for eg. on the 99 row, for the (1/4) circle it say {row 98} and for the remaining circle it says {row 99}. the deviation increases as the number of rows increases.
protected override CanvasCell GetCanvasCellAt(int x, int y)
{
Rectangle rect = GetImageViewPort();
Point pt = new Point(x, y);
CanvasCell c = new CanvasCell() { Row = -1, Column = -1 };
if (rect.Contains(pt))
{
double zoomedCircleSize = CircleSize * ZoomFactor;
Point p = pt;// PointToClient(new Point(x, y));
p.X -= (int)(rect.X + (AutoScrollPosition.X) );
p.Y -= (int)(rect.Y + (AutoScrollPosition.Y));
int row = (int)((p.Y) / (zoomedCircleSize));
//row = (int)((p.Y + (row * ZoomFactor)) / zoomedCircleSize);
int col;
if (row % 2 != 0)
{
if (p.X >= 0 && p.X < (zoomedCircleSize / 2))
{
col = -1;
}
else
col = (int)((p.X - (zoomedCircleSize / 2)) / zoomedCircleSize);
}
else
{
if (p.X > (zoomedCircleSize * cols))
{
col = -1;
}
else
{
col = (int)((p.X) / zoomedCircleSize);
}
}
//if (!GetRectangle(row, col).ContainsWithInBoundingCircle(p))
//{
// c.Column = -1;
// c.Row = -1;
//}
//else
{
c.Column = col;
c.Row = row;
}
}
//
return c;
}
hope i was clear in explaining my problem.
EDIT:
the VERTICAL_PIXEL_OFFSET is 1 and the circle size is 16

I also posted this on msdn, Stefan Hoffmann was kind enough to post an SSCCE of how to do that. Basically the idea was to precalculate the honeycombs, as #usr suggested in the comments section.
Here is the link to MSDN post.

A quick observation: do you have to use circles - would hexagons simplify the problem?