I am making a drawing application where I want user to allow gradient color when they draw line .. ccDraw allows the color but how to get gradient color ?
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I want to create a PNG image with transparency.
QImage image(dim, dim, QImage;;Format_ARGB32);
And I set the
qRgba(qRed, qGreen, qBlue, alpha)
But the alpha channel does not modify the transparency/opacity of the color, instead modify the intensity color (from white to color).
Thus, how can I set the transparency of the QImage (which I save on file)?
I have to use QImage, no other stuff.
How do you expect to see the transparency? Ordinary image viewers like photo viewers in Windows and Linux are painting the image on a white canvas. That's why the transparent pixels are being blended with white color. Look at the pictures below :
White background with no transparency on the circle:
The same circle with 50% opacity on white background:
The circle with transparency on a grid background:
That is why advanced image editors like Photoshop, are using such canvas as their default background.
I have a QTableWidget. I want to have alternating background colors for the rows, but I can't use QTableWidget::setAlternatingRowColors because I need one color for two rows and the other one for the next two and so on (see the below image).
Thus, when I add a QTableWidgetItem, I set the according background color manually by QTableWidgetItem::setBackground().
But I don't get a "flat" or "plain" background by this, but a gradient and rounded corners:
I would like to have the background color all over the cells, without further "decoration". How can I get rid of this?
When you select a single color as the background (QBrush constructed from a QColor), the style engine tries to render a styled background, which in your case draws this gradient with border.
You can trick the style engine by using a QBrush constructed from a QImage, so the render engine draws exactly that image and nothing more. In your case, use an image with a single pixel, namely the color you want as the background. For this, construct a 1x1-sized QImage and set the color of the pixel using fill, then use that image as a brush:
// Create the image (using the default image format)
QImage img(QSize(1, 1), QImage::Format_ARGB32_Premultiplied);
// Set the color, here light gray:
img.fill(QColor(224, 224, 224));
// Apply the image as the background for the item:
item->setBackground(QBrush(img));
I am drawing a shadow on a CCLableTTF using CGContextSetShadowWithColor. I have set the colour to be white but i always get a grey/black line around the edge of the shadow.
Is there anyway to remove the outline, i have looked but i cannot see any stroke colour for the shadow.
Thanks
I'm trying to show only a part of a background image (game scenenario in the future). The basic way to work is for example, first I draw a background image, after that i need to "hide"/cover the image with some dark or darness (no light, don't know what option must be chosen) and use the mouse click to using a circle or a triangle (my options) show only the part of the image background over with the circle/triangle centered on mouse position. I called this "lantern effect".
First Option: Play with the alpha channel, creating a an square covering all the window size and after that trying to substract the circle area over the alpha square over the image.
Second Option: Play again with a black square covering all the image background and trying to substract a circle/triangle. Try with glLogicOp but this method only plays mixing colors. Don't know how to do operation with 2D polygons with OpenGL.
...
Any other idea or easy example to learn how to do something similar.
Image example:
That's quite easy to achieve actually:
Create black texture with your lantern light shape in Alpha channel. (Texture could be animated)
Render background.
Render Lantern texture centered at your in-game mouse cursor.
Render black padding around the lantern texture to hide everything around till screen edges.
There's no need to use any special blending modes, just an overlay.
I am attempting to use Textured fonts as so that I can display text in my openGL scene. However I am having trouble finding glBlendFunc values that will work.
The background that the text will be placed on is a grayscale image but will change throughout the execution. Because the background changes the text could possibly be on top of any color from black to white.
The best values I have found are glBlendFunc(Gl.GL_SRC_COLOR, Gl.GL_ONE_MINUS_SRC_ALPHA). This will make the black box surrounding the character disappear but the character itself will fade as the background goes towards white.
Please help!
Do you want the text to invert based on the background color? white text over black background, black text on white? I think you can achieve an invert via blendfunc.
Alternatively you can use a font texture which has a "border" built into it to help set the character apart from the background. Imagine a white font w/ a smooth alpha blended black "glow". The font will look good against almost all colors.