I have to draw a String on a transparent bitmap at first, then draw A to destination canvas.
However on certain case, there is black border around the characters.
Bitmap* tempImg = new Bitmap(1000, 1000, PixelFormat32bppARGB);
Graphics tempGr(tempImg);
tempGr.Clear(Color(0, 255,255,255));
Gdiplus::SolidBrush* brush = new SolidBrush(Color(255, 255, 0, 0 ));
Gdiplus::FontFamily fontFamily(L"Times New Roman");
Gdiplus::Font* font = new Gdiplus::Font(&fontFamily, 19, FontStyleRegular, UnitPixel);
RectF rec(400, 400, 1000, 10000);
tempGr.DrawString(
L"Merry Chrismas",
-1,
font,
rec,
NULL,
brush
);
Graphics desGr(hdc);
desGr.Clear(Color::Gray);
desGr.DrawImage(tempImg , 0,0, 1000, 1000);
The character draw on desGr have black board for some fontsize.
How can I avoid this problem?
Many thanks!
I think the problem here is that you are drawing the text onto a transparent background.
You could try adding this line after the call to tempGr.Clear...
tempGr.TextRenderingHint = TextRenderingHint.AntiAlias;
ps - sorry not sure the exact syntax in C++ ;)
I just solved this problem in XNA:
Clear background to the same as the foreground color. The only difference is that the background should have Alpha=0, and the foreground with Alpha >> 0
The black border comes from blending of your background and foreground of different colors. Try to clear the background to some contrasting color to fully appreciate the phenomenon.
Related
I had tried to fill the color outside of the actual image but fails to do so. I get the pixmap as the input.
QRect target = AlignRect(aRect, iPixmap.size(), Alignment());
aPainter.drawPixmap(target, iPixmap);
QPainter painter(&iPixmap);
painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
painter.setBrush(QColor::fromRgb(43, 174, 255));
painter.setPen(QColor::fromRgb(43, 174, 255));
painter.drawRect(target);
I get the below image as the pixmap.
I want to fill the color outside the white icon like
Can someone give the pointer for the same?
This can be done easily because your iPixmap has a transparent background...
You can draw a rect at 0,0 with a WIDTH and HEIGH of the widgets size and then after that place the X on top of that.
example:
painter.drawRect(0,0,w,h);
I'm working on a MFC project with some GDI drawings.
I use DC.DrawText to draw a vertical text into a DC using a LOGFONT with lfEscapement = 900.
The text is output when i use DT_NOCLIP in the desired vertical formatting.
However to center this text i used a call to DC.DrawText with the DT_CALCRECT argument.
I recognized that, despite the text is indeed drawn vertically, the CRect has a larger width
than height.
My intuition says me that a vertical drawn text should have a larger height than width.
I did not include the calculation for centering the text. The question is just about what i can rely upon when i implement that vertical centering.
Does DC.DrawText with DT_CALCRECT ignore escapement?
void CMFCFontTestDlg::OnPaint()
{
CPaintDC dc(this); // Gerätekontext zum Zeichnen
if (IsIconic())
{
...
}
else
{
CDialogEx::OnPaint();
CRect clTextRect;
CFont myFont;
myFont.CreateFont(12, 0, 900, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, _T("Tahoma"));
CFont* oldFont = dc.SelectObject(&myFont);
dc.DrawText(_T("000000"), clTextRect, DT_CALCRECT);
clTextRect.MoveToXY(100, 100);
dc.DrawText(_T("000000"), clTextRect, DT_NOCLIP);
dc.SelectObject(oldFont);
}
}
I found out about it in the remarks to the DrawTextEx function
https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-drawtextexa.
However, please note that neither the documentation of DrawText does say anything about this nor the documentation of the DT_CALCRECT flag.
This is likely to be overseen if one uses DrawText and not DrawTextEx.
I informed MS about this via "Is this page helpful?" feedback possibility.
Remarks
The DrawTextEx function supports only fonts whose escapement and
orientation are both zero.
The text alignment mode for the device context must include the
TA_LEFT, TA_TOP, and TA_NOUPDATECP flags.
Considering this the solution is to use some trigonometric calculation starting from the size determined for escapement = 0 and then calculate the topleft and bottomright points of the rotated rect.
I'm using a self compiled of OpenCv 3.3 with OPENGL and CUDA enabled on Windows 7.
I'm having trouble to display an image in fullscreen mode without any border.
I use the following minimal example for my test:
// Name of window
std::string name = "Test Window";
// Create window
cv::namedWindow(name, CV_WINDOW_OPENGL | cv::WINDOW_NORMAL);
cvSetWindowProperty(name.c_str(), CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
// Create a frame at resolution
cv::Size size = cv::Size(1920, 1080);
cv::cuda::GpuMat emptyFrame;
cv::Mat frame(size, CV_8UC(3));
// Fill it in blue
cv::rectangle(frame, cv::Rect(0, 0, size.width, size.height), cv::Scalar(255, 0, 0), CV_FILLED);
emptyFrame.upload(frame);
// Size window to full resolution
cv::resizeWindow(name, size.width, size.height);
while(1)
{
// Display an empty frame
cv::imshow(name, emptyFrame);
cv::waitKey(40);
}
This code show me a full screen windows paint in blue, however it remain a ONE pixel border on top and left border:
Grey left and top border
The border seem not to be the border as explained here:
https://stackoverflow.com/a/38494752/1570628
In fact it's the background of the main window created by OpenCv.
Digging into OpenCv code, it effectivelly create 2 windows inside cvNamedWindow function:
mainhWnd = CreateWindow( "Main HighGUI class", name, defStyle | WS_OVERLAPPED, rect.x, rect.y, rect.width, rect.height, 0, 0, hg_hinstance, 0 );
if( !mainhWnd )
CV_ERROR( CV_StsError, "Frame window can not be created" );
ShowWindow(mainhWnd, SW_SHOW);
//YV- remove one border by changing the style
hWnd = CreateWindow("HighGUI class", "", (defStyle & ~WS_SIZEBOX) | WS_CHILD, CW_USEDEFAULT, 0, rect.width, rect.height, mainhWnd, 0, hg_hinstance, 0);
if( !hWnd )
CV_ERROR( CV_StsError, "Frame window can not be created" );
So the 'border' we saw is the mainhWnd (Main HighGUI class) color.
However, it mean that my displayed image in blue is shifted by one pixel to the rigth and bottom of my screen, so I loose 1 line of pixel on bottom and right side because they overflow the screen.
I can see that it's the case because on a dual screen I can see the right line of pixel overflow on my second screen. More over, if I draw an horizontal line to the last line of my image, it doesn't appear, same occur on vertical line for last column of my image.
For testing solution, I tried to change style of mainhWnd and hWnd directly in OpenCv code by using many combination of flags, also testing using WS_POPUP, but anyway I always have this top and left border.
I also tried solution here but it do not remove the border:
https://stackoverflow.com/a/6512315/1570628
Do anyone have a clue for my problem?
Regards.
Hey this worked for me (at least it did on python, and since you just have to change a flag, i believe this will work for you too)
Change this flag "CV_WINDOW_OPENGL | cv::WINDOW_NORMAL)" to this flag "WINDOW_FREERATIO"
And voila! Problem Solved
http://msdn.microsoft.com/en-us/library/sa8ahz7h(v=vs.80).aspx
//Border
CPen pen;
pen.CreatePen(PS_DASH, 20, RGB(0, 0, 0));
CPen* penOld = dc.SelectObject(&pen);
dc.Rectangle(rect);
dc.FillRect(rect, &brush);
How does this code work? It draws a rectangle and then a border around it. I just can't get my head around it.
When you ask the device context to draw a rectangle, it will use the current Pen.
You can set the current Pen, Brush, clipping region or whatever using the SelectObject() method. You're basically saying "use this Pen from now on".
SelectObject() also returns the item it was using before, so that it doesn't get lost and leak memory, and you can put it back later if you want. This is why penOld is being saved to a variable in your code. It will probably be selected back again later on.
CPen pen; //declare a new Pen object
pen.CreatePen(PS_DASH, 20, RGB(0, 0, 0)); //Create the GDI Pen, dashed, 20 pixels wide, black.
CPen* penOld = dc.SelectObject(&pen); //Tell the DC to use this pen from now on.
dc.Rectangle(rect); //Draw a rectangle (using the current pen)
dc.FillRect(rect, &brush); //Fill a rectangle (using the current brush)
It creates a pen, selects it into the DC, and then instructs the DC to use the pen (which is 20 pixels wide) to draw a rectangle at the specified coordinates. It then fills in the inside of that rectangle with a brush.
in a C++ MFC application. using the dc of ( CPaintDC dc(this); )
How do i draw a rectangle ( LPRECT ) with an alpha transparency that i can adjust.?
Following is an example c# code which i need to convert into C++
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
Color color = Color.FromArgb(75,Color.Red); //sets color Red with 75% alpha transparency
Rectangle rectangle = new Rectangle(100,100,400,400);
g.FillRectangle(new SolidBrush(color), rectangle); //draws the rectangle with the color set.
}
You need to look into GDI+. Its a bit of a faff but you can create a "Graphics" object as follows:
Gdiplus::Graphics g( dc.GetSafeHdc() );
Gdiplus::Color color( 192, 255, 0, 0 );
Gdiplus::Rect rectangle( 100, 100, 400, 400 );
Gdiplus::SolidBrush solidBrush( color );
g.FillRectangle( &solidBrush, rectangle );
Don't forget to do
#include <gdiplus.h>
and to call
GdiplusStartup(...);
somewhere :)
You'll notice it's pretty damned similar to your C# code ;)
Its worth noting that the 75 you put in your FromArgb code doesn't set 75% alpha it actually sets 75/255 alpha or ~29% alpha.
GDI (and thus MFC) has no decent support for drawing with an alpha. But GDI+ is available in C++ code as well. Use #include <gdiplus.h> and initialize it with GdiplusStartup(). You can use the Graphics class, create one with its Graphics(HDC) constructor from your CPaintDC. And use its FillRectangle() method. The SDK docs are here.
int StartHoriz,StartVert,BarWidth,BarHeight; // rect start, width and height
StartHoriz=0;
StartVert=100;
width = 100;
height=120;
CDC* pCDC = GetDC(); // Get CDC pointer
CRect Rect(StartHoriz,StartVert,BarWidth,BarHeight); //create rectangle dimensions
pCDC->Rectangle(Rect); //draw rectangle