cairo_move_to (cr, x, y);
cairo_show_text (cr, "hello");
You know, will draw a parallel text to the axis, but now, I want to draw a slanted text somewhat like this:
but avoid cairo_rotate,I have two point, start point and end point, Tell me how to do, thanks
Cairo is not meant for that; use Pango. Other than cairo_rotate, you don't really have any options in Cairo. As the linked page states, Cairo has only a toy text API.
Related
I'm trying to draw some basic graphics here. Namely, Lines or Rectangles with exact pixel widths. No fancy anti aliasing or anything else that makes the line appear different.
Can someone give me some instructions or basic code that can achieve this?
I used the basic Line/Rectangle functions and adjusted the width parameter and the color was black.
Here's what solid 2px and 1px lines look like in any graphics program:
And here's what it looks like in Kivy:
The Kivy version has a thicker line and a 1 pixel line that is not black. How do i draw pixel perfect lines?
Due to an ancient design mistake, the width property in Kivy actually controls half the line width, as you have observed, with the exception of width 1 in which case the line is drawn using a plain OpenGL instruction and genuinely has width 1 pixel. No, this doesn't make sense.
If you get blurriness after specifying half the width you really need, this is probably because of OpenGL interpolation when the line doesn't actually line up with the display pixels. If you have an example where it seems particularly bad, it might be possible to say more about that.
Following Quote from this source:
http://www.cambridgeincolour.com/tutorials/image-projections.htm
Equirectangular image projections map the latitude and longitude
coordinates of a spherical globe directly onto horizontal and vertical
coordinates of a grid, where this grid is roughly twice as wide as it
is tall.
I have a 13312 px width and 6656 pixel height Panorama picture. It's a equirectangular projection of a room and have a 2:1 ratio.
I use following formular to calculate the xPosition:
var xPosition = ( panorama.width / 360 ) * azimuth
Azimuth = Phi = Heading = Angle to the left or right
How do I project this now on a 1366x768px browser screen?
I think my results are wrong, because it's not on the point where it should be.. it could be because the sphere has a distortion on the left and right:
Is there any formular to calculate the position with attention to the distortion and scale it to fit on the browser screen? I looked many (MANY) sources to find a solution for this, but they always just say that equirectangular are just lat and long.. they don't consider the distortion.
Last question: To find a special solution, I tryed to put a plane on the circle and expanded the line which shows the alpha angle. I though with Phytagoras I could find the position.. but this didn't worked either.. maybe I did something wrong? Is this the way even possible or am I doing it wrong?
edit
THIS is what I'm actually looking for: http://othree.github.io/360-panorama/three-2d/
The black grid in the background. What is the name of this? For what do I have to google or look for? When you start the 2D Panorama, if you want to get the coordinations of the top right corner of the window, what do you have to do?
The whole calculation problem was about to create a Google Streetview similiar view from a 2:1 equirectangular image. We already found a solution for this with a great help from Martin Matysiak (https://github.com/marmat | Google).
It's been a while so I can't give a direct answer to what the main solution is, but I can provide a URL to an AddOn Martin wrote for adding the custom Markers that we actually were trying to make.
You can follow https://github.com/marmat/google-maps-api-addons and look for yourself. In the end it helped a lot to solve the main problem and let us continue with our main Framework for Google Business Tours.
If you follow the link in the threejs demo you included, it would take you to the source code.
particularly look at:
https://github.com/mrdoob/three.js/blob/dev/examples/webgl_panorama_equirectangular.html
and
https://github.com/mrdoob/three.js/blob/dev/src/geometries/SphereBufferGeometry.js
not sure if there is distortion though. The distortion comes from the fact that the texture is mapped to the sphere, and the sphere is rendered in 3D (openGL).
I want to draw a thick point or a dot in the client area of an mfc alpplication. Is there a function to do so? Alternatively I could even draw an extremely small circle and fill it with a colour to make it appear as a dot- but again how do I fill an object? especially a curved one?
Then I also want to put some text next to it- so what function could i use to "write" in the client area?
GetDC()->SetPixel(x, y, RGB(1,2,3))
Where GetDC() will return the current CWnd's device context, (x,y) are the coordinates, and RGB() is the red/greed/blue color.
Look at GetDC()->Ellipse() for a circle, etc. and GetDC()->TextOut() for displaying text.
It would be good to become familiar with device contexts in general, see:
MFC CDC Members
I have a multiviewport OpenGL modeler application. It has three different viewports : perspective, front and top. Now I want to paint a label for each viewport and not succeeding in doing it.
What is the best way to print a label for each different perspective?
EDITED : The result
Here is the result of my attempt:
I don't understand why the perspective viewport label got scrambled like that. And, Actually I want to draw it in the upper left corner. How do I accomplished this, because I think it want 3D coordinate... is that right? Here is my code of drawing the label
glColor3f(1,0,0);
glDisable(GL_DEPTH_TEST);
glDepthMask(GL_FALSE);
glRasterPos2f(0,0);
glPushAttrib(GL_LIST_BIT); // Pushes The Display List Bits
glListBase(base - 32); // Sets The Base Character to 32
glCallLists(strlen("Perspective"), GL_UNSIGNED_BYTE, "Perspective"); // Draws The Display List Textstrlen(label)
glPopAttrib();
I use the code from here http://nehe.gamedev.net/data/lessons/lesson.asp?lesson=13
thanks
For each viewport switch into a projection that allows you to supply "viewport space" coordinates, disable depth testing (glDisable(GL_DEPTH_TEST)) and depth writes (glDepthMask(GL_FALSE)) and draw the text using one of the methods used to draw text in OpenGL (texture mapped fonts, rendering the full text into a texture drawing that one, draw glyphs as actual geometry).
Along with #datenwolf's excellent answer, I'd add just one bit of advice: rather than drawing the label in the viewport, it's usually easier (and often looks better) to draw the label just outside the viewport. This avoids the label covering anything in the viewport, and makes it easy to get nice, cleanly anti-aliased text (which you can normally do in OpenGL as well, but it's more difficult).
If you decide you need to draw the text inside the viewport anyway, I'll add just one minor detail to what #datenwolf said: since you generally do want your text anti-aliased (even if the rest of the picture isn't) you generally want to draw the label after all the other geometry of the picture itself. If you haven't turned on anti-aliasing otherwise, you generally will want to turn it on for drawing the text.
I'm not sure how to ask this but here goes.
I draw a filled coloured rectangle on screen. The colour is in form of R,G,B
I then want to draw text on top of the rectangle, however the colour of the text has to be such that it provides the best contrast, meaning it's readable.
Example:
If I draw a black rectangle, the obvious colour for text would be white.
What I tried right now is this. I pass this function the colour of the rectangle and it returns an inverted colour that I then use for my text.
It works, but it's not the best way.
Any suggestions?
// eg. usage: Color textColor = GetInverseLuminance(rectColor);
private Color GetInverseLuminance(Color color)
{
int greyscale = (int)(255 - ((color.R * 0.30f) + (color.G * 0.59f) + (color.B * 0.11f)));
return Color.FromArgb(greyscale, greyscale, greyscale);
}
One simple approach that is guaranteed to give a significantly different color is to toggle the top bit of each component of the RGB triple.
Color inverse(Color c)
{
return new Color(c.R ^ 0x80, c.G ^ 0x80, c.B ^ 0x80);
}
If the original color was #1AF283, the "inverse" will be #9A7203.
The contrast will be significant. I make no guarantees about the aesthetics.
Update, 2009/4/3: I experimented with this and other schemes. Results at my blog.
The most readable color is going to be either white or black. The most 'soothing' color will be something that is not white nor black, it will be a color that lightly contrasts your background color. There is no way to programmatically do this because it is subjective. You will not find the most readable color for everyone because everyone sees things differently.
Some tips about color, particularly concerning foreground and background juxtaposition, such as with text.
The human eye is essentially a simple lens, and therefore can only effectively focus on one color at a time. The lenses used in most modern cameras work around this problem by using multiple lenses of different refractive indexes (chromatic lenses) so that all colors are in focus at one time, but the human eye is not that advanced.
For that reason, your users should only have to focus on one color at a time to read the text. This means that either the foreground is in color, or the background, but never both. This leads to a condition typically called vibration, in which the eye rapidly shifts focus between foreground and background colors, trying to resolve the shape, but it never resolves, the shape is never in focus, and it leads to eyestrain.
Your function won't work if you supply it with RGB(127,127,127), because it will return the exact same colour. (modifying your function to return either black or white would slightly improve things)
The best way to always have things readable is to have white text with black around it, or the other way around.
It's oftenly achieved by first drawing black text at (x-1,y-1),(x+1,y-1),(x+1,y-1),(x+1,x+1), and then white text at (x,y).
Alternatively, you could first draw a semi-transparent black block, and then non-transparent white text over it. That ensures that there will always be a certain amount of contrast between your background and your text.
why grey? either black or white would be best. white on dark colors, black on light colors. just see if luminance is above a threshold and pick one or the other
(you don't need the .net, c# or asp.net tags, by the way)
You need to study some color theory. A program called "Color Wheel Pro" is fun to play around with and will give you the general idea.
Essentially, you're looking for complimentary colors for a given color.
That said, I think you will find that while color theory helps, you still need a human eye to fine tune.