I'm building an app with a Print Preview function. If the printer does not support color, I want to render everything in grayscale. I depend on 3P rendering libraries where I can't change the color they render with.
Without resorting to rendering to an offscreen bitmap, and then converting it to grayscale, etc... is there any way to just tell GDI+ to render grayscale?
There is no such possibility to tell the Graphics object to draw in grayscale (afaik).
You have three possibilities:
1) Render to an offscreen image (what you don't want)
2) Make a screenshot of your current render result and convert it to grayscale and draw it over your current render result (not a nice solution in my eyes)
3) Tweak your current rendering code and convert all used colors to grayscale
To convert a color to grayscale you can use this code:
public Color ToGrayScaleColor(Color originalColor)
{
int grayScale = (int)((originalColor.R * .3) + (originalColor.G * .59) + (originalColor.B * .11));
return Color.FromArgb(grayScale, grayScale, grayScale);
}
Code found and adjusted from http://csharp-me.blogspot.com/2014/01/convert-color-to-gray-scale-in-c-c-sharp.html
Related
I'm using Qt3D with a combination of this offscreen renderer and modified the framegraph to include a background image, like here.
Unfortunately, adding transparency to the objects drawn over the background image using QPhongAlphaMaterial only works unsatisfactorily.
This is th result:
What you can't see here is that the whole circle part is actually transparent, i.e. the renderer wrote the transparency value of the object for the whole pixel instead of adding it transparently on top of the background.
This is what the rendered object looks like wihtout transparency:
And this is the background:
The framegraph has two branches: one for the backgroun image, which is processed first, and one for the objects. I added a QRenderStateSet for the objects that contains a QBlendEquation with the blend function set to add and a QBlendEquationArguments with source RGB and alpha set to 1, and destination RGB and alpha set to 1 minus source alpha.
Any ideas how to fix this problem?
(For anyone wondering, I took the images from the T-Less dataset and wrote a program to create ground-truth data for 6D pose estimation)
Similarly to this question, the format of the texture that is being rendered to needs to be set to RGB8_UNorm and not RGBA8_UNorm, i.e. without the alpha channel.
I'm building a custom control that fakes partially-rounded rectangles by drawing several rectangles on top of each other. I want to use a colour in this control that is sourced dynamically from elsewhere -- and sometimes that colour has an alpha component (semi-transparent). Of course, that doesn't work at all for me, since the multiple rectangles situation means that the alpha will show the rectangles layering.
Is there a function I can use to set the alpha part of a colour to full opacity and leave the rest of the colour alone?
You can access and set individual color components, like this:
someColor.a = 1 // set alpha to 1 for opaque
If you are asking about getting a pixel's value after the renderer has blended everything, there is no efficient way to do it.
If you know all colors that are blended, you can mix them manually.
You can define a function to do that in javascript (or same in C++):
function makeTransparent(color, alphaPercent) {
return color.a *= alphaPercent;
}
and use it as:
Rectangle {
property color myColor: "#33000000" //<-- e.g. semi-transparent black
color: makeTransparent(mycolor, 1.2);
}
Note: my function makes color transparent in percent as Qt.darker() and Qt.lighter()
I have a transparent QGraphicsWebview inside a QGraphicsView with the following settings:
The QGraphicsView is the high level widget, and is shown in full screen mode
The graphics view uses a QGLWidget as its view port (to use opengl-es)
Alpha channel and double buffering are enabled in this QGLWidget
Transparency is achieved by graphicsView->setStyleSheet("background:transparent")
Following attributes are set for QGraphicsView and QGraphicsWebview
WA_TranslucentBackground = true
WA_NoSystemBackground = true
WA_OpaquePaintEvent = false
The QPalette::Base and QPalette::Window brushes of webview and webview->page() are set to Qt::transparent
At the beginning, the transparency works fine. But as the screen get updated (when I scroll), it looks like the new bitmap is blended on top of the existing one to get a superimposed picture. After about 5-6 screen updates, this blending causes the colors to accumulate and form an opaque rectangle (with a corrupted image). Following images show first, second and final stages of the problem.
How do I tell qt/opengl to stop blending and just draw the new image to the frame buffer?
I tried calling fillRect(boundRect(), Qt::transparent) from overridden Webview::paint and GraphicsView::paintEvent; but it didn't work except for making the updates slower.
I am new to Qt and OpenGl, so I might be missing some basic flags or settings.
I tried all the methods mentioned above. They did not work for me. I then debugged into qtbase code and found that setting the Opacity level make the top browser layer transparent.
this->setOpacity(0.1);
this pointer points to the QGraphicsWebView object.
With this method, the whole front browser contents including background will be transparent. To separate header, paragraph and background and to specify different transparent levels for them, I will have to dig into webkit code a little further to figure out the problem. But for now, setOpacity() did the trick and is good enough for what I am doing.
It turns out the problem is graphicsView->setStyleSheet("background:transparent");. Who would have guessed?!
Yeah, the line that I thought made transparency work was actually causing troubles with transparency. The application works fine without that line (or if you change it to background:none)
In short, steps to get a transparent QGraphicsWebview using QGLWidget:
Set the Base palettes of QGraphicsWebview, QWebpage and the outer QGraphicsView to Qt::transparent
scene->setBackgroundBrush(QBrush(Qt::transparent));
You should also make sure that html body background is set to transparent values:
html, body {
background-color: rgba(127, 127, 0, 0.5);
}
I have a image declared like the following:
[Bindable]
[Embed( source="assets/banana.png" )]
public var iconBANANA : Class;
It is involving into itemRenderer, but I wish to change the color of the image when some event occurs (like clicking above or something).
The rest of the objects used the image shall remain unchanged, only the object on which the event has occurred shall change the color of the image.
But the biggest question is :
How to change the image color mainly - like there is a Blue area on image - to turn it on Green, or Yellow ?
I believe what you're looking for are Filters. What you're explaning (changing one color to another) is not exactly trivial and going into some fairly complex image manipulation but you can get some results using the ColorMatrixFilter.
You're looking for beginBitmapFill.
I have a handful of sprites that I am attempting to group together via addChild().
Here is some pseudo-code demonstrating what I would like to accomplish:
import nav.text.TextSprite;
spr1:Sprite = new Sprite();
spr1.graphics.clear();
spr1.graphics.beginFill(0x000000);
spr1.graphics.drawRect(0,0,100,100);
txt1:TextSprite = new TextSprite;
txt1.text = "hello";
spr1.addChild(txt1);
//this is what isn't working: the sprite is hidden but not the text
spr1.alpha = 0.0;
For some reason I cannot seem to get the TextSprite to draw correctly... All it is is a Sprite with a TextField added to it. I think everything is working there, but I might have something wrong w/r/t making sure all of TextSprites children are grouped correctly.
I should mention that it does position correctly; but the alpha property won't respond in the way I would expect it to. I.E., the sprite that the TextField is attached to will allow it's alpha to be set but the text remains visible.
Any thoughts?
Most likely you just need to embed the font in your textfield. Try changing the x, y of spr1 and see if txt1 moves along with it. If it truly is a child then it will respond to the new position.
You need to embed the font using textfield.embedFonts = true. If your text is disappearing when you do this, how are you going about embedding the font (using the Flex embed meta tag or using the Flash IDE?), check that you are not changing the font weight (setting the text to bold when you have only embedded the normal weight font) and if you are using a text format, be sure to apply the text format AFTER you set the textfield.text property. You can get around this by using textfield.defaultTextFormat.