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I am writing an extension / widgets for gnome-shell.So I want to show some information using text. Actually I want to put text in middle of the circle using pangoCairo but I can't figure out how can I put text using pangoCairo?
here is my code of drawing circles with a function to set text middle of the circles but the text is not showing in the middle.
draw_stuff(canvas, cr, width, height) {
cr.setSourceRGBA(1,1,1,0.2);
cr.save ();
cr.setOperator (Cairo.Operator.CLEAR);
cr.paint ();
cr.restore ();
cr.setOperator (Cairo.Operator.OVER);
cr.scale (width, height);
cr.setLineCap (Cairo.LineCap.BUTT);
//test
cr.setLineWidth (0.08);
cr.translate (0.5, 0.5);
cr.arc (0, 0, 0.4, 0, Math.PI * 2);
cr.stroke ();
cr.setSourceRGBA(1,1,1,0.8);
cr.rotate(-Math.PI/2);
cr.save();
cr.arc (0,0, 0.4, 0, this.currentR /100 * 2 * Math.PI);
cr.stroke();
cr.setSourceRGBA(1,1,1,0.9);
cr.save();
cr.arc (0,0, 0.25, 0, 2 * Math.PI);
cr.fill();
cr.moveTo(0, 0);
cr.setSourceRGBA(0,0,0,0.9);
cr.save();
this.text_show(cr, "WoW");
cr.restore();
return true; }
update() { this.currentR = 60;
this._canvas.connect ("draw", this.draw_stuff.bind(this));
this._canvas.invalidate();}
text_show(cr, showtext, font = "DejaVuSerif Bold 16") {
let pl = PangoCairo.create_layout(cr);
pl.set_text(showtext, -1);
pl.set_font_description(Pango.FontDescription.from_string(font));
PangoCairo.update_layout(cr, pl);
let [w, h] = pl.get_pixel_size();
cr.relMoveTo(-w / 2, 0);
PangoCairo.show_layout(cr, pl);
cr.relMoveTo(w / 2, 0);}
I dont know what's wrong here?
let [w, h] = pl.get_pixel_size();
cr.relMoveTo(-w / 2, 0);
You are placing your text something like 1000 pixels off the screen. get_pixel_size() is documented as:
pango_layout_get_size() returns the width and height scaled by PANGO_SCALE.
and PANGO_SCALE has the value 1024:
Thus, you need to change the code above to
let [w, h] = pl.get_pixel_size();
cr.relMoveTo(-w / 2048, 0);
Bonus points for not hardcoding the value of PANGO_SCALE and instead getting it from your Pango API bindings. However, for that I don't know enough about gnome-shell-extensions. Is this code in Javascript? Dunno.
# Kepler's Laws.py
# plots the orbit of a planet in an eccentric orbit to illustrate
# the sweeping out of equal areas in equal times, with sun at focus
# The eccentricity of the orbit is random and determined by the initial velocity
# program uses normalised units (G =1)
# program by Peter Borcherds, University of Birmingham, England
from vpython import *
from random import random
from IPython import display
import pandas as pd
def MonthStep(time, offset=20, whole=1): # mark the end of each "month"
global ccolor # have to make it global, since label uses it before it is updated
if whole:
Ltext = str(int(time * 2 + dt)) # end of 'month', printing twice time gives about 12 'months' in 'year'
else:
Ltext = duration + str(time * 2) + ' "months"\n Initial speed: ' + str(round(speed, 3))
ccolor = color.white
label(pos=planet.pos, text=Ltext, color=ccolor,
xoffset=offset * planet.pos.x, yoffset=offset * planet.pos.y)
ccolor = (0.5 * (1 + random()), random(), random()) # randomise colour of radial vector
return ccolor
scene = display(title="Kepler's law of equal areas", width=1000, height=1000, range=3.2)
duration = 'Period: '
sun = sphere(color=color.yellow, radius=0.1) # motion of sun is ignored (or centre of mass coordinates)
scale = 1.0
poss = vector(0, scale, 0)
planet = sphere(pos=poss, color=color.cyan, radius=0.02)
while 1:
velocity = -vector(0.7 + 0.5 * random(), 0, 0) # gives a satisfactory range of eccentricities
##velocity = -vector(0.984,0,0) # gives period of 12.0 "months"
speed = mag(velocity)
steps = 20
dt = 0.5 / float(steps)
step = 0
time = 0
ccolor = color.white
oldpos = vector(planet.pos)
ccolor = MonthStep(time)
curve(pos=[sun.pos, planet.pos], color=ccolor)
while not (oldpos.x > 0 and planet.pos.x < 0):
rate(steps * 2) # keep rate down so that development of orbit can be followed
time += dt
oldpos = vector(planet.pos) # construction vector(planet.pos) makes oldpos a varible in its own right
# oldpos = planet.pos makes "oldposs" point to "planet.pos"
# oldposs = planet.pos[:] does not work, because vector does not permit slicing
denom = mag(planet.pos) ** 3
velocity -= planet.pos * dt / denom # inverse square law; force points toward sun
planet.pos += velocity * dt
# plot orbit
curve(pos=[oldpos, planet.pos], color=color.red)
step += 1
if step == steps:
step = 0
ccolor = MonthStep(time)
curve(pos=[sun.pos, planet.pos], color=color.white)
else:
# plot radius vector
curve(pos=[sun.pos, planet.pos], color=ccolor)
if scene.kb.keys:
print
"key pressed"
duration = 'Duration: '
break
MonthStep(time, 50, 0)
label(pos=(2.5, -2.5, 0), text='Click for another orbit')
scene.mouse.getclick()
for obj in scene.objects:
if obj is sun or obj is planet: continue
obj.visible = 0 # clear the screen to do it again
I copied Kepler's Laws code in google and compiled it on pycharm.
But there is an error that
scene = display(title="Kepler's law of equal areas", width=1000, height=1000, range=3.2)
TypeError: 'module' object is not callable
I found some information on google that "pandas" library can improve this error so I tried it but I can't improve this error.
What should I do?
Replace "display" with "canvas", which is the correct name of this entity.
I've written a small 2D engine in opengl in the process of making a game. I'm using OpenGL ES 2 and the code compiles and runs on iOS and Mac OSX.
Now I'm extending it to support 3D and I'm having a problem setting up the camera.
I've checked the code a hundred times and I can't finde where the problem is, so maybe someone with experience on this can give an idea.
This is the code I have: I'm posting the part of the code where I think the problem might be, but if something else is needed just ask me.
Matrix4 _getFrustumMatrix(float left, float right, float bottom, float top, float near, float far){
Matrix4 res = Matrix4(2.0 * near / (right - left), 0, 0, 0,
0, 2.0 * near / (top - bottom), 0, 0,
(right + left) / (right - left), (top + bottom) / (top - bottom), -(far + near) / (far - near), -1.0,
0,0, -2.0 * far * near / (far - near), 0);
return res;
}
Matrix4 _getPerspectiveMatrix(float near, float far, float angleOfView){
static float aspectRatio = float(SCREENW)/float(SCREENH);
float top = near * tan(angleOfView * 3.1415927 / 360.0);
float bottom = -top;
float left = bottom * aspectRatio;
float right = top * aspectRatio;
return _getFrustumMatrix(left, right, bottom, top, near, far);
}
Matrix4 _getLookAtMatrix(Vector3 eye, Vector3 at, Vector3 up){
Vector3 forward, side;
forward = at - eye;
forward.normalize();
side = forward ^ up;
side.normalize();
up = side ^ forward;
Matrix4 res = Matrix4(side.x, up.x, -forward.x, 0,
side.y, up.y, -forward.y, 0,
side.z, up.z, -forward.z, 0,
0, 0, 0, 1);
res.translate(Vector3(0 - eye));
return res;
}
void Scene3D::_deepRender(){
cameraEye = Vector3(10,0,40);
cameraAt = Vector3(0,0,0);
cameraUp = Vector3(0,1,0);
MatrixStack::push();
Matrix4 projection = _getPerspectiveMatrix(1, 100, 45);
Matrix4 view = _getLookAtMatrix(cameraEye, cameraAt, cameraUp);
MatrixStack::set(projection * view);
Space3D::_deepRender();
MatrixStack::pop();
}
The drawn object is a representation of the axes where x=red, y=green, z=blue, and it's located at (0,0,0).
If I put the eye at (0,0,40) everything looks as expected:
If I put the eye at (10,0,40) then the object is not drawn in the middle of the screen as it should be.
This is the Matrix4::translate method:
void Matrix4::translate(const Vector3& v) {
a14 += a11 * v.x + a12 * v.y + a13 * v.z;
a24 += a21 * v.x + a22 * v.y + a23 * v.z;
a34 += a31 * v.x + a32 * v.y + a33 * v.z;
a44 += a41 * v.x + a42 * v.y + a43 * v.z;
}
EDIT: To add some information:
Using _getLookAtMatrix() with this parameters:
cameraEye = Vector3(40,40,40);
cameraAt = Vector3(0,0,0);
cameraUp = Vector3(0,1,0);
Should give me an equivalent matrix to this one?
Matrix4 view;
view.setIdentity();
view.translate(Vector3(0,0,-69.2820323)); // 69.2820323 is the length of Vector3(40,40,40)
view.rotate(45, Vector3(1,0,0));
view.rotate(-45, Vector3(0,1,0));
At least those transformations makes sense to me and the resulting image looks as what I should expect.
But this matrix compared to the one I get using _getLookAtMatrix() are very different:
view:
0.707106769, -0.49999997, 0.49999997, 0,
0, 0.707106769, 0.707106769, 0,
-0.707106769, -0.49999997, 0.49999997, 0,
0, 0, -69.2820358, 1
_getLookAtMatrix(cameraEye, cameraAt, cameraUp):
0.707106769, 0, -0.707106769, 0,
-0.408248276, 0.816496551, -0.408248276, 0,
0.577350259, 0.577350259, 0.577350259, 0,
-35.0483475, -55.7538719, 21.520195, 1
You seem to have some serious ordering inconsistencies in your matrix class.
For example I assumed your Matrix4 constructor takes it arguments (the matrix elements) as column-major, otherwise your functions wouldn't match the reference implementations of glFrustum and gluLookAt and you would get completely screwed results.
And the code of your translate function also looks correct, since it has to modify the last column of the matrix, which are the elements (a14, a24, a34 and a44).
But the your print out of the view matrix suggests that translate actually modifies the last row, unless you print the matrix in column-major format and therefore transposed. But in this case the print of the _getLookAtMatrix suggests that the Matrix4 constructor takes its arguments in row-major order, which indeed invalidates other things.
Of course all this is also depending on how you send the matrices to OpenGL and how you use them in the vertex shader (I assume ES 2.0, otherwise there would be no need for your own matrix library). If you indeed use ES 1 then you need to send the matrix elements to OpenGL in column-major order, but the translation has to be in the last column and not the last row.
But no matter what convention you use, there is definitely a severe inconsistency inside your matrix code. But without seeing the whole Matrix4 class, the vertex shader and the code where you upload the matrices to OpenGL, it is hard to tell where this inconsistency is.
I have a bunch of drawing areas (they are actually cairo surfaces, but I don't think it matters too much) in a scrolled window, and I would like to refresh the drawings. However, when I redraw the images, they are not shown till I scroll the window up and down. After that the figures are correct, so I have to conclude that the drawing routine itself is proper. I have also included a
while Gtk.events_pending():
Gtk.main_iteration()
loop to wait for all pending operations, but that does not solve the problem. Could someone point out to me what else is missing?
Thanks,
v923z
OK, so the larger chunks of the code. First, a class defining the a drawing area onto which I am going to paint (note that the body is not indented properly! I don't know how to indent larger pieces of code here):
class Preview:
def __init__(self):
self.frame = Gtk.Frame()
self.frame.set_shadow_type(Gtk.ShadowType.IN)
self.frame.show()
self.da = Gtk.DrawingArea()
self.da.set_size_request(200, 300)
self.da.connect('configure-event', self.configure_event)
self.da.connect('draw', self.on_draw)
self.frame.add(self.da)
self.da.show()
def configure_event(self, da, event):
allocation = da.get_allocation()
self.surface = da.get_window().create_similar_surface(cairo.CONTENT_COLOR,
allocation.width,
allocation.height)
cairo_ctx = cairo.Context(self.surface)
cairo_ctx.set_source_rgb(1, 1, 1)
cairo_ctx.paint()
return True
def on_draw(self, da, cairo_ctx):
cairo_ctx.set_source_surface(self.surface, 0, 0)
cairo_ctx.paint()
return True
pass
Next, the point where I actually create the drawing area. viewport_preview is a viewport created in glade.
self.previews = []
self.widget('viewport_preview').remove(self.vbox_preview)
self.vbox_preview = Gtk.VBox(homogeneous=False, spacing=8)
self.widget('viewport_preview').add(self.vbox_preview)
self.vbox_preview.show()
for page in self.pages:
preview = Preview()
self.vbox_preview.pack_start(preview.frame, False, False, 10)
self.previews.append(preview)
while Gtk.events_pending():
Gtk.main_iteration()
self.draw_preview(None)
return True
Then the function drawing the previews. This is really just a wrapper for the next function, and I needed this only because if I delete one entry in the previews, then I have to handle that case. I believe, the while loop at the end of this function is not necessary, for it will be at the end of the next one anyway.
def draw_preview(self, counter=None):
if counter is not None:
self.vbox_preview.remove(self.previews[counter].frame)
self.previews.pop(counter)
self.pages.pop(counter)
self.vbox_preview.show()
while Gtk.events_pending():
Gtk.main_iteration()
for i in range(len(self.pages)):
self.draw_note(self.previews[i].da, self.previews[i].surface, self.pages[i])
while Gtk.events_pending():
Gtk.main_iteration()
Finally, the drawing function itself:
def draw_note(self, widget, surface, page):
list_pos = '%d/%d'%(self.page + 1, len(self.pages))
self.widget('label_status').set_text(list_pos)
cairo_ctx = cairo.Context(surface)
cairo_ctx.set_source_rgb(page.background[0], page.background[1], page.background[2])
cairo_ctx.paint()
width, height = widget.get_size_request()
xmin, xmax, ymin, ymax = fujitsu.page_size(page)
factor = min(height / (2.0 * self.margin + ymax - ymin), width / (2.0 * self.margin + xmax - xmin))
factor *= 0.8
page.scale = factor
value = self.widget('adjustment_smooth').get_value()
#print value
for pen in page.pagecontent:
x = self.margin + pen.path[0][0] - xmin
y = self.margin + pen.path[0][1] - ymin
cairo_ctx.move_to(x * factor, y * factor)
if self.widget('checkbutton_smooth').get_active() == False:
[cairo_ctx.line_to((self.margin + x - xmin) * factor,
(self.margin + y - ymin) * factor) for x, y in pen.path]
else:
bezier_curve = bezier.expand_coords(pen.path, value)
x = self.margin + bezier_curve[0][0][0] - xmin
y = self.margin + bezier_curve[0][0][1] - ymin
cairo_ctx.move_to(x * factor, y * factor)
[cairo_ctx.curve_to((self.margin + control[1][0] - xmin) * factor,
(self.margin + control[1][1] - ymin) * factor,
(self.margin + control[2][0] - xmin) * factor,
(self.margin + control[2][1] - ymin) * factor,
(self.margin + control[3][0] - xmin) * factor,
(self.margin + control[3][1] - ymin) * factor)
for control in bezier_curve]
cairo_ctx.set_line_width(pen.thickness * self.zoom_factor)
cairo_ctx.set_source_rgba(pen.colour[0], pen.colour[1], pen.colour[2], pen.colour[3])
cairo_ctx.stroke()
cairo_ctx.rectangle(0, height * 0.96, width, height)
cairo_ctx.set_source_rgba(page.banner_text[0][0], page.banner_text[0][1], page.banner_text[0][2], page.banner_text[0][3])
cairo_ctx.fill()
cairo_ctx.move_to(width * 0.05, height * 0.99)
cairo_ctx.show_text(self.filename + ' ' + list_pos)
cairo_ctx.set_font_size(self.zoom_factor * 10.0)
xbearing, ybearing, twidth, theight, xadvance, yadvance = (cairo_ctx.text_extents(page.banner_text[3]))
cairo_ctx.move_to(width - 1.03 * twidth, height * 0.99)
cairo_ctx.show_text(page.banner_text[3])
cairo_ctx.set_source_rgba(0, 0, 0.9, 0.90)
cairo_ctx.stroke()
rect = widget.get_allocation()
widget.get_window().invalidate_rect(rect, False)
while Gtk.events_pending():
Gtk.main_iteration()
I think that's about it.
You could use gtk_widget_queue_draw_area or gdk_window_invalidate_rect.This will mark the widget (or rectangle) as dirty and once the main loop is idle expose event will be received where in you can redraw. From you description it appears the updates are happening on expose event so these APIs might be of use. Also you can check this sample from the cairo site where in you can see the usage of gtk_widget_queue_draw_area.
I have not used pygtk but from Google I found that the corresponding call for gtk_widget_queue_draw_area is gtk.Widget.queue_draw_area & for gdk_window_invalidate_rect is gtk.gdk.Window.invalidate_rect
Hope this helps!
Actually, I thought that there would be an easy way to achieve that. What I need is pure alpha value information. For testing, I have a 50 x 55 px PNG, where on every edge a 5x5 pixel rectangle is fully transparent. In these areas alpha has to be 0.Everywhere else it has to be 255. I made very sure that my PNG is created correctly, and it also looks correctly.
Please tell me if this is theoretically correct:
I created an CGImageRef that has only the alpha channel and nothing else. This is done with CGBitmapContextCreate and kCGImageAlphaOnly as param.
CGBitmapContextGetBitsPerPixel(context) returns me 1, so it indicates me that I really have only one component per pixel: The desired alpha value.
I've been reading that CGBitmapContextCreate will handle all the conversion from the given image to the new created context. My image was previously PNG-24 with transparency, but pngcrunch from Xcode seems to convert them somehow.
So, just in theory: Do I have any chance to get to the correct, unpremultiplied alpha at this point? The values I get seem to almost match, but in a big 5x5 transparent square I get values like 19, 197, 210, 0, 0, 0, 98 and so on. If they were true, I would have to see something from the image. The image itself is solid blue.
Premultiplication doesn't affect the alpha channel, it affects the color channels.
The formula for raster compositing (putting one raster image over another) is:
dst.r = src.r * src.a + dst.r * (1.0 - src.a);
dst.g = src.g * src.a + dst.g * (1.0 - src.a);
dst.b = src.b * src.a + dst.b * (1.0 - src.a);
Premultiplication cuts out the first multiplication expression:
dst.r = src.r′ + dst.r * (1.0 - src.a);
dst.g = src.g′ + dst.g * (1.0 - src.a);
dst.b = src.b′ + dst.b * (1.0 - src.a);
This works because the source color components are already multiplied by the alpha component—hence the name “premultiplied”. It doesn't need to multiply them now, because it already has the results.
unpremultiplied alpha
The alpha component itself is never premultiplied: What would you multiply it by? The color components are premultiplied by the alpha.
Since premultiplying color values is a simple as:
r = (r * a) / 255;
g = (g * a) / 255;
b = (b * a) / 255;
Getting the inverse would be:
if (a > 0) {
r = (r * 255) / a;
g = (g * 255) / a;
b = (b * 255) / a;
}
This formular is not correct. The goal is to find unmultiplexed (r, g, b) that would latter result to the same multiplexed values (it is not possible to find the original r, g, b values, though.
However with the formular above we find for the example of
alpha = 100
r_premulti = 1
a reconstructed r = 2;
Latter if this r is multiplexed again we find 2 * 100 / 255 = 0 but we wanted r_premulti == 1 instead!!
The correct formular needs to round up. Example for r-component:
reconstruced r = ceiling(r_premulti * 255 / alpha)