Develop Reference

Can't convert Bitmap to IplImage

I'm trying to make an image cropping tool.
I am following this https://www.codeproject.com/Articles/703519/Cropping-Particular-Region-In-Image-Using-Csharp
But since it's a bit old and the plugin/DLL's it uses have changed I have been trying to adapt his code from OpenCvSharp 2.0 to OpenCvSharp 2.4
When I'm converting the bitmaps to IplImages and using Cv.Mul() it gives me this error:
Attempted to read or write protected memory. This is often an indication that other memory is corrupt
I have never used OpenCvSharp other ways of creating the IplImage even reading the IplImage from a written image.
Code:
public static IplImage BitmapToIplImage(Bitmap bitmap)
{
IplImage tmp, tmp2;
System.Drawing.Rectangle bRect = new System.Drawing.Rectangle(new System.Drawing.Point(0, 0), new System.Drawing.Size((int)bitmap.Width, (int)bitmap.Height));
BitmapData bmData = bitmap.LockBits(bRect, ImageLockMode.ReadWrite, bitmap.PixelFormat);
tmp = Cv.CreateImage(Cv.Size(bitmap.Width, bitmap.Height), BitDepth.U8, 3);
tmp2 = Cv.CreateImage(Cv.Size(bitmap.Width, bitmap.Height), BitDepth.U8, 1);
byte[] data = new byte[Math.Abs(bmData.Stride * bmData.Height)];
tmp.SetData(bmData.Scan0, data.Length);
bitmap.UnlockBits(bmData);
// Cv.CvtColor(tmp, tmp2, ColorConversion.RgbToGray);
return tmp;
}
private void CropImage()
{
IplImage ipl = Cv.CreateImage(new CvSize(curBmp.Width, curBmp.Height), BitDepth.U8, 3);
Graphics ga = Graphics.FromImage(curBmp);
ga.FillRectangle(new SolidBrush(System.Drawing.Color.Black), new System.Drawing.Rectangle(0, 0, curBmp.Width, curBmp.Height));
SolidBrush brush = new SolidBrush(System.Drawing.Color.FromArgb(1, 1, 1));
curGraphics.FillClosedCurve(brush, imagePoints.ToArray());
Cv.Mul(BitmapToIplImage(curOgBmp), BitmapToIplImage(curBmp), ipl, 1);
ComputeCrop();
Stream s = null;
ipl.ToStream(s, ".png", null);
curBmp = new Bitmap(s);
RefreshImageViewer();
}
-----------------------------EDIT-----------------------------------------
I tried to follow what Markus posted, and I got it to work without any errors in the code.
Although the image cropped is a bit strange here are the methods I use, plus the RefreshImageViewer that is how I put the bitmap in the image control.
I have been trying to see if I missed something for hours, but I think not.
Output example: Imgur image link
Code:
public void RefreshImageViewer()
{
bmpSource = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
curBmp.GetHbitmap(),
IntPtr.Zero,
System.Windows.Int32Rect.Empty,
BitmapSizeOptions.FromWidthAndHeight(curBmp.Width, curBmp.Height));
imageViewer.Source = bmpSource;
curGraphics = Graphics.FromImage(curBmp);
}
private void CropImage()
{
Graphics Ga = Graphics.FromImage(curBmp);
//the black image
Ga.FillRectangle(new SolidBrush(System.Drawing.Color.Black), new System.Drawing.Rectangle(0, 0, curBmp.Width, curBmp.Height));
//draw from the last point to first point
Ga.DrawLine(new System.Drawing.Pen(System.Drawing.Color.Red, 3), imagePoints[imagePoints.Count - 1], imagePoints[0]);
//all of the rgb values are being set 1 inside the polygon
SolidBrush Brush = new SolidBrush(System.Drawing.Color.FromArgb(1, 1, 1));
//we have to prepare one mask of Multiplying operation for cropping region
curGraphics.FillPolygon(Brush, imagePoints.ToArray());
Mat accc = (BitmapToMat(curOgBmp).Mul(BitmapToMat(curBmp))).ToMat();
System.Drawing.Rectangle r = ComputeCrop();
curBmp = accc.ToBitmap().Clone(r, curOgBmp.PixelFormat);
RefreshImageViewer();
}
private System.Drawing.Rectangle ComputeCrop()
{
int smallestX = curBmp.Width, biggestX = 0, biggestY = 0, smallestY = curBmp.Height;
for (int i = 0; i < imagePoints.Count; i++)
{
biggestX = Math.Max(biggestX, imagePoints[i].X);
smallestX = Math.Min(smallestX, imagePoints[i].X);
biggestY = Math.Max(biggestY, imagePoints[i].Y);
smallestY = Math.Min(smallestY, imagePoints[i].Y);
}
System.Drawing.Rectangle rectCrop = new System.Drawing.Rectangle(smallestX, smallestY, biggestX - smallestX, biggestY - smallestY);
return rectCrop;
}
public static Mat BitmapToMat(Bitmap bitmap)
{
Mat tmp, tmp2;
System.Drawing.Rectangle bRect = new System.Drawing.Rectangle(new System.Drawing.Point(0, 0), new System.Drawing.Size((int)bitmap.Width, (int)bitmap.Height));
BitmapData bmData = bitmap.LockBits(bRect, ImageLockMode.ReadWrite, bitmap.PixelFormat);
tmp2 = new Mat(new OpenCvSharp.Size(bitmap.Width, bitmap.Height), MatType.CV_8U);
tmp = new Mat(bitmap.Height, bitmap.Width, MatType.CV_8UC3, bmData.Scan0);
bitmap.UnlockBits(bmData);
return tmp;
}

“IplImage” ist the old image container from OpenCv 1. As Andreas already mentioned, today you should use “Mat” instead. Have also a look here : Difference between cvMat, Mat and IpImage
Unfortunately, your code sample is not complete, hence I corrected the two methods from the original project ( https://www.codeproject.com/Articles/703519/Cropping-Particular-Region-In-Image-Using-Csharp).
The following methods are tested and work as intended in the original project in combination with the latest OpenCVSharp version (v4.x) . It should be very simple now to convert the changes to your code.
public static Mat BitmapToIplImage(Bitmap bitmap)
{
Mat tmp, tmp2;
Rectangle bRect = new Rectangle(new System.Drawing.Point(0, 0), new System.Drawing.Size((int)bitmap.Width, (int)bitmap.Height));
BitmapData bmData = bitmap.LockBits(bRect, ImageLockMode.ReadWrite, bitmap.PixelFormat);
tmp2 = new Mat(new Size(bitmap.Width, bitmap.Height), MatType.CV_8U);
tmp = new Mat(bitmap.Height, bitmap.Width, MatType.CV_8UC3, bmData.Scan0);
bitmap.UnlockBits(bmData);
return tmp;
}
private void crop()
{
timer1.Stop();
Graphics Ga = Graphics.FromImage(bmp);
//the black image
Ga.FillRectangle(new SolidBrush(Color.Black), new Rectangle(0, 0, bmp.Width, bmp.Height));
//draw from the last point to first point
Ga.DrawLine(new Pen(Color.Red, 3), polygonPoints[polygonPoints.Count - 1], polygonPoints[0]);
//all of the rgb values are being set 1 inside the polygon
SolidBrush Brush = new SolidBrush(Color.FromArgb(1, 1, 1));
//we have to prepare one mask of Multiplying operation for cropping region
G.FillClosedCurve(Brush, polygonPoints.ToArray());
var accc= (BitmapToIplImage(Source).Mul(BitmapToIplImage(bmp))).ToMat();
computecrop();
croplast = accc.ToBitmap().Clone(rectcrop, Source.PixelFormat);//just show cropped region part of image
pictureBox2.Image = croplast; // crop region of image
}

Is there another way to export a frame in ffmpeg to a texture2d? My code working in Windows but not Linux

Sound is working in Linux the same as it did in Windows. But the video is just a black screen and when I attempt to save the frames as BMP files all of them were corrupt/empty files. I am using Ffmpeg.Autogen to interface with the libraries. https://github.com/Ruslan-B/FFmpeg.AutoGen. The file is VP8 and OGG in a MKV container. Though the extension is AVI for some reason.
I tried messing with the order of the code a bit. I checked to make sure the build of Ffmpeg on Linux had VP8. I was searching online but was having trouble finding another way to do what I am doing. This is to contribute to the OpenVIII project. My fork-> https://github.com/Sebanisu/OpenVIII
This just preps the scaler to change the pixelformat or else people have blue faces.
private void PrepareScaler()
{
if (MediaType != AVMediaType.AVMEDIA_TYPE_VIDEO)
{
return;
}
ScalerContext = ffmpeg.sws_getContext(
Decoder.CodecContext->width, Decoder.CodecContext->height, Decoder.CodecContext->pix_fmt,
Decoder.CodecContext->width, Decoder.CodecContext->height, AVPixelFormat.AV_PIX_FMT_RGBA,
ffmpeg.SWS_ACCURATE_RND, null, null, null);
Return = ffmpeg.sws_init_context(ScalerContext, null, null);
CheckReturn();
}
Converts Frame to BMP
I am thinking this is where the problem is. Because I had added bitmap.save to this and got empty BMPs.
public Bitmap FrameToBMP()
{
Bitmap bitmap = null;
BitmapData bitmapData = null;
try
{
bitmap = new Bitmap(Decoder.CodecContext->width, Decoder.CodecContext->height, PixelFormat.Format32bppArgb);
AVPixelFormat v = Decoder.CodecContext->pix_fmt;
// lock the bitmap
bitmapData = bitmap.LockBits(new Rectangle(0, 0, Decoder.CodecContext->width, Decoder.CodecContext->height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
byte* ptr = (byte*)(bitmapData.Scan0);
byte*[] srcData = { ptr, null, null, null };
int[] srcLinesize = { bitmapData.Stride, 0, 0, 0 };
// convert video frame to the RGB bitmap
ffmpeg.sws_scale(ScalerContext, Decoder.Frame->data, Decoder.Frame->linesize, 0, Decoder.CodecContext->height, srcData, srcLinesize); //sws_scale broken on linux?
}
finally
{
if (bitmap != null && bitmapData != null)
{
bitmap.UnlockBits(bitmapData);
}
}
return bitmap;
}
After I get a bitmap we turn it into a Texture2D so we can draw it.
public Texture2D FrameToTexture2D()
{
//Get Bitmap. there might be a way to skip this step.
using (Bitmap frame = FrameToBMP())
{
//string filename = Path.Combine(Path.GetTempPath(), $"{Path.GetFileNameWithoutExtension(DecodedFileName)}_rawframe.{Decoder.CodecContext->frame_number}.bmp");
//frame.Save(filename);
BitmapData bmpdata = null;
Texture2D frameTex = null;
try
{
//Create Texture
frameTex = new Texture2D(Memory.spriteBatch.GraphicsDevice, frame.Width, frame.Height, false, SurfaceFormat.Color); //GC will collect frameTex
//Fill it with the bitmap.
bmpdata = frame.LockBits(new Rectangle(0, 0, frame.Width, frame.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);// System.Drawing.Imaging.PixelFormat.Format32bppArgb);
byte[] texBuffer = new byte[bmpdata.Width * bmpdata.Height * 4]; //GC here
Marshal.Copy(bmpdata.Scan0, texBuffer, 0, texBuffer.Length);
frameTex.SetData(texBuffer);
}
finally
{
if (bmpdata != null)
{
frame.UnlockBits(bmpdata);
}
}
return frameTex;
}
}
I can post more if you want it's pretty much all up on my fork
Video will play back as it does in Windows. As smooth as 15 fps can be. :)

I ended up removing the bitmap part of the code. And it worked! So previously I would convert the frame to a bitmap and it would copy the pixels out of the bitmap into the Texture2D. I looked closer and realized I could skip that step of the bitmap. I'm sorry for not being clear enough on my question.
/// <summary>
/// Converts Frame to Texture
/// </summary>
/// <returns>Texture2D</returns>
public Texture2D FrameToTexture2D()
{
Texture2D frameTex = new Texture2D(Memory.spriteBatch.GraphicsDevice, Decoder.CodecContext->width, Decoder.CodecContext->height, false, SurfaceFormat.Color);
const int bpp = 4;
byte[] texBuffer = new byte[Decoder.CodecContext->width * Decoder.CodecContext->height * bpp];
fixed (byte* ptr = &texBuffer[0])
{
byte*[] srcData = { ptr, null, null, null };
int[] srcLinesize = { Decoder.CodecContext->width * bpp, 0, 0, 0 };
// convert video frame to the RGB data
ffmpeg.sws_scale(ScalerContext, Decoder.Frame->data, Decoder.Frame->linesize, 0, Decoder.CodecContext->height, srcData, srcLinesize);
}
frameTex.SetData(texBuffer);
return frameTex;
}

Draw a transparent line using native win32 gdi

I am drawing lines by using win32 gdi native apis. Now, I want to draw the line as transparent. I have set the alpha channel property in the color. However, setting the alpha channel in color is not drawing the line as transparent. I read about Alpha Blend Api but could not figure out the solution.
var hdc = g.GdiDeviceContext;
var srcHdc = CreateCompatibleDC(hdc);
var clipRegion = CreateRectRgn(x, y, x + width, y + height);
SelectClipRgn(hdc, clipRegion);
var pen = CreatePen(PenStyle.Solid, LineWidth, (uint)ColorTranslator.ToWin32(colour));
if (pen != IntPtr.Zero)
{
var oldPen = SelectObject(hdc, pen);
Polyline(hdc, points, points.Length);
SelectObject(hdc, oldPen);
DeleteObject(pen);
}
SelectClipRgn(hdc, IntPtr.Zero);
AlphaBlend(hdc, x, y, width, height, srcHdc, x, y, width, height, new BlendFunction(0x00, 0, 0x7f, 0x00));
DeleteObject(clipRegion);
I am trying to draw the line as transparent.

var srcHdc = CreateCompatibleDC(hdc);
This creates a memory device context. This is the right first step. But the memory dc is not ready yet. It requires a memory bitmap as well.
SelectObject(hdc, pen);
Polyline(hdc, points, points.Length);
This will draw on windows device context. But we want to draw on memory device context, and then draw the memory on to HDC using AlphaBlend
See example below:
int w = 100;
int h = 100;
//create memory device context
var memdc = CreateCompatibleDC(hdc);
//create bitmap
var hbitmap = CreateCompatibleBitmap(hdc, w, h);
//select bitmap in to memory device context
var holdbmp = SelectObject(memdc, hbitmap);
//begine drawing:
var hpen = CreatePen(0, 4, 255);
var holdpen = SelectObject(memdc, hpen);
Rectangle(memdc, 10, 10, 90, 90);
//draw memory device (memdc) context on to windows device context (hdc)
AlphaBlend(hdc, 0, 0, w, h, memdc, 0, 0, w, h, new BLENDFUNCTION(0, 0, 128, 0));
//clean up:
SelectObject(memdc, holdbmp);
SelectObject(memdc, holdpen);
DeleteObject(hbitmap);
DeleteObject(hpen);
DeleteDC(memdc);

Multisampled FBO is ignoring depth testing

I have modified my rendering engine to use multisampled textures, except now depth testing is being ignored.
Here's how I'm creating the multisampled FBO,
public MSAA_FBO(int WindowWidth, int WindowHeight)
{
this.width = WindowWidth;
this.height = WindowHeight;
GL.GenFramebuffers(1, out ID);
GL.BindFramebuffer(FramebufferTarget.Framebuffer, ID);
// Colour texture
GL.GenTextures(1, out textureColorBufferMultiSampled);
GL.BindTexture(TextureTarget.Texture2DMultisample, textureColorBufferMultiSampled);
GL.TexImage2DMultisample(TextureTargetMultisample.Texture2DMultisample, 4, PixelInternalFormat.Rgb8, WindowWidth, WindowHeight, true);
GL.FramebufferTexture2D(FramebufferTarget.Framebuffer, FramebufferAttachment.ColorAttachment0, TextureTarget.Texture2DMultisample, textureColorBufferMultiSampled, 0);
// Depth render buffer
GL.GenRenderbuffers(1, out RBO);
GL.BindRenderbuffer(RenderbufferTarget.RenderbufferExt, RBO);
GL.RenderbufferStorageMultisample(RenderbufferTarget.Renderbuffer, 4, RenderbufferStorage.DepthComponent, WindowWidth, WindowHeight);
GL.BindRenderbuffer(RenderbufferTarget.Renderbuffer, 0);
var status = GL.CheckFramebufferStatus(FramebufferTarget.Framebuffer);
Console.WriteLine("MSAA: " + status);
GL.BindFramebuffer(FramebufferTarget.Framebuffer, 0);
}
performing the resolve,
public void resolveToFBO(FBO outputFBO)
{
GL.BindFramebuffer(FramebufferTarget.DrawFramebuffer, outputFBO.ID);
GL.BindFramebuffer(FramebufferTarget.ReadFramebuffer, this.ID);
GL.BlitFramebuffer(0, 0, this.width, this.height, 0, 0, outputFBO.width, outputFBO.height, ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit, BlitFramebufferFilter.Nearest);
}
and rendering the image,
public void MSAAPass(Shader shader)
{
GL.UseProgram(shader.ID);
GL.BindFramebuffer(FramebufferTarget.Framebuffer, MSAAbuffer.ID);
GL.Viewport(0, 0, Width, Height);
GL.Enable(EnableCap.Multisample);
GL.ClearColor(System.Drawing.Color.Black);
GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
GL.Enable(EnableCap.DepthTest);
GL.Disable(EnableCap.Blend);
// Uniforms
Matrix4 viewMatrix = player.GetViewMatrix();
GL.UniformMatrix4(shader.getUniformID("viewMatrix"), false, ref viewMatrix);
// Draw all geometry
DrawScene(shader);
GL.BindFramebuffer(FramebufferTarget.Framebuffer, 0);
MSAAbuffer.resolveToFBO(testBuffer);
}

Your multisampled FBO does not have a depth buffer, hence the depth test will not work. Although you actually created a multisampled renderbuffer with GL_DEPTH_COMPONENT format, you forgot to attach this one as the GL_DEPTH_ATTACHMENT of your FBO. You need to add a glFramebufferRenderbuffer() call in your MSAA_FBO() function.

How to paint over a bitmap with a brush - C#/.NET

This seems like it should be simple, but I can't seem to find any way to do it. I have a custom WinForms control that has an overridden paint method that does some custom drawing.
I have a Bitmap in memory, and all I want to do is paint over the whole thing with a HashBrush, but preserve the alpha channel, so that the transparent parts of the bitmap don't get painted.
The bitmap in memory is not a simple shape, so it will not be feasible to define it as a set of paths or anything.
EDIT: In response to showing the code, there is a lot of code in the paint routine, so I'm only including a relevant snippet, which is the method in question. This method gets called from the main paint override. It accepts a list of images which are black transparency masks and combines them into one, then it uses a ColorMatrix to change the color of the combined image it created, allowing it to be overlayed on top of the background. All I want to accomplish is being able to also paint hashmarks on top of it.
private void PaintSurface(PaintEventArgs e, Image imgParent, List<Image> surfImgs, Rectangle destRect, ToothSurfaceMaterial material)
{
using (Bitmap bmp = new Bitmap(imgParent.Width, imgParent.Height,
System.Drawing.Imaging.PixelFormat.Format32bppPArgb))
{
using (Graphics g = Graphics.FromImage(bmp))
{
foreach (Image img in surfImgs)
{
g.DrawImage(img, System.Drawing.Point.Empty);
}
}
ColorMatrix matrix = new ColorMatrix(
new float[][] {
new float[] { 0, 0, 0, 0, 0},
new float[] { 0, 0, 0, 0, 0},
new float[] { 0, 0, 0, 0, 0},
new float[] { 0, 0, 0, 0.7f, 0},
new float[] { material.R / 255.0f,
material.G / 255.0f,
material.B / 255.0f,
0, 1}
});
ImageAttributes imageAttr = new ImageAttributes();
imageAttr.SetColorMatrix(matrix);
Rectangle r = GetSizedRect(imgParent, destRect);
e.Graphics.DrawImage(bmp,
r,
0,
0,
bmp.Width,
bmp.Height,
GraphicsUnit.Pixel, imageAttr);
}
}

The solution I ended up using was the following method. First I combine the individual masks into one, then create a new Bitmap and paint the whole thing with the HatchBrush, finally iterate through the mask and set the alpha values on the newly generated bitmap based on the mask.
private Bitmap GenerateSurface(Image imgParent, List<Image> surfImgs, ToothSurfaceMaterial material)
{
Bitmap mask = new Bitmap(imgParent.Width, imgParent.Height,
System.Drawing.Imaging.PixelFormat.Format32bppPArgb);
using (Graphics g = Graphics.FromImage(mask))
{
foreach (Image img in surfImgs)
{
g.DrawImage(img, System.Drawing.Point.Empty);
}
}
Bitmap output = new Bitmap(mask.Width, mask.Height,
System.Drawing.Imaging.PixelFormat.Format32bppPArgb);
using (Graphics g = Graphics.FromImage(output))
{
if (material.HatchStyle != null)
{
HatchBrush hb = new HatchBrush((HatchStyle)material.HatchStyle, material.FgColor, material.BgColor);
g.FillRectangle(hb, new Rectangle(0, 0, output.Width, output.Height));
}
else
{
SolidBrush sb = new SolidBrush(material.FgColor);
g.FillRectangle(sb, new Rectangle(0, 0, output.Width, output.Height));
}
}
var rect = new Rectangle(0, 0, output.Width, output.Height);
var bitsMask = mask.LockBits(rect, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
var bitsOutput = output.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
unsafe
{
int offset = 0;
for (int y = 0; y < mask.Height; y++)
{
byte* ptrMask = (byte*)bitsMask.Scan0 + y * bitsMask.Stride;
byte* ptrOutput = (byte*)bitsOutput.Scan0 + y * bitsOutput.Stride;
for (int x = 0; x < mask.Width; x++)
{
offset = 4 * x + 3;
ptrOutput[offset] = (byte)(ptrMask[offset] * 0.7);
}
}
}
mask.UnlockBits(bitsMask);
output.UnlockBits(bitsOutput);
return output;
}

I think you don't need any ColorMatrix which is overkill, you just need a ColorMap, here is the code which may not suit your requirement but should give you the idea. That's because I possibly don't understand your problem well, if you have any problem, just leave some comment and I'll try to improve the answer:
ImageAttributes imgA = new ImageAttributes();
ColorMap cm = new ColorMap();
cm.OldColor = Color.Black
cm.NewColor = Color.FromArgb((byte)(0.7*255), Color.Green);
imgA.SetRemapTable(new ColorMap[] {cm });
GraphicsUnit gu = GraphicsUnit.Pixel;
g.DrawImage(imageToDraw,new Point[]{Point.Empty,
new Point(backImage.Width/2,0),
new Point(0,backImage.Height/2)},
Rectangle.Round(imageToDraw.GetBounds(ref gu)),
GraphicsUnit.Pixel, imgA);
the new Point[] is an array of 3 Points used to locate the destination Rectangle.
The code above is used to Draw the imageToDraw on top of the backImage and convert and color of Black to the color Green with Opacity = 70%. That's what you want to fulfill your code.
UPDATE
This may be what you want, in fact your code doesn't show what you want, it just shows what you have which doesn't implement anything related to your problem now. I deduce this from your very first description in your question. The input is an image with background color (which will be made partially transparent later) being Black. Now the output you want is an image with all the non-Black region being painted with a HatchBrush. This output will then be processed to turn the Black background to a partially transparent background.
public void PaintHatchBrush(Bitmap input, HatchBrush brush){
using(Graphics g = Graphics.FromImage(input)){
g.Clip = GetForegroundRegion(input, Color.Black);
GraphicsUnit gu = GraphicsUnit.Pixel;
g.FillRectangle(brush, input.GetBounds(ref gu));
}
}
//This is implemented using `GetPixel` which is not fast, but it gives you the idea.
public Region GetForegroundRegion(Bitmap input, Color backColor){
GraphicsPath gp = new GraphicsPath();
Rectangle rect = Rectangle.Empty;
bool jumpedIn = false;
for (int i = 0; i < bm.Height; i++) {
for (int j = 0; j < bm.Width; j++) {
Color c = bm.GetPixel(j, i);
if (c != backColor&&!jumpedIn) {
rect = new Rectangle(j, i, 1, 1);
jumpedIn = true;
}
if (jumpedIn && (c == backColor || j == bm.Width - 1)) {
rect.Width = j - rect.Left;
gp.AddRectangle(rect);
jumpedIn = false;
}
}
}
return new Region(gp);
}
//Usage
HatchBrush brush = new HatchBrush(HatchStyle.Percent30, Color.Green, Color.Yellow);
PaintHatchBrush(yourImage, brush);
//then yourImage will have HatchBrush painted on the surface leaving the Black background intact.
//This image will be used in the next process to turn the Black background into 70%
//opacity background as you did using ColorMatrix (or more simply using ColorMap as I posted previously)