问题描述
社区.
我知道这里有很多答案，互联网上的手册，教程和参考资料，还有更多关于此问题的信息.我也知道线性代数的知识是必需的.但是，当我花时间思考所有的理论并解决实践中的练习时，我的头开始跳动，我无法做最简单的事情:(
请，如果您知道一些快速的解决方案，如何在渲染之前使文本在其中心旋转-请告诉我，请求证.
现在我有:
#...
cr.move_to(*text_center)
myX, myY = text_center[0] - (width / 2), text_center[1] + (height / 2)
cr.save()
cr.translate(myX, myY)
cr.rotate(radians(text_angle))
cr.show_text(letter)
cr.restore()
#...
但是我的信并没有自动旋转.就像掉到右边一样:(我知道我的代码不正确.也许我错过了转换，但是我不知道如何正确处理.
更新:不幸的是，文本不受翻译的影响，所以
cr.translate(10000, 10000)
cr.rotate(radians(15))
cr.show_text("hello")
将与
完全相同cr.rotate(radians(15))
cr.show_text("hello")
而且我不知道如何在不制作新表面或其他东西(例如图形处理器中的新层)的情况下使文本围绕其中心旋转:(
至少在我的计算机上可用的cairo版本(1.8.8)上，以下方法适用于我:
def text(ctx, string, pos, theta = 0.0, face = 'Georgia', font_size = 18):
ctx.save()
# build up an appropriate font
ctx.select_font_face(face , cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
ctx.set_font_size(font_size)
fascent, fdescent, fheight, fxadvance, fyadvance = ctx.font_extents()
x_off, y_off, tw, th = ctx.text_extents(string)[:4]
nx = -tw/2.0
ny = fheight/2
ctx.translate(pos[0], pos[1])
ctx.rotate(theta)
ctx.translate(nx, ny)
ctx.move_to(0,0)
ctx.show_text(string)
ctx.restore()
可以通过以下方式使用:
width = 500
height = 500
surface = cairo.ImageSurface(cairo.FORMAT_RGB24, width, height)
ctx = cairo.Context(surface)
ctx.set_source_rgb(1,1,1)
rect(ctx, (0,0), (width, height), stroke=False)
ctx.set_source_rgb(0,0,0)
for i in xrange(5):
for j in xrange(5):
x = 100 * i + 20
y = 100 * j + 20
theta = math.pi*0.25*(5*i+j)
text(ctx, 'hello world', (x, y), theta, font_size=15)
surface.write_to_png('text-demo.png')
community.
I know that there are many answers here, manuals, tutorials and references over the internets and amny more about this question. Also I know that knowledge of linear algebra is required.But when I think about time to figuring out all the theory and solving exercises in practice - my head is blowing off and I can't do the simplest things :(
Please, if you know a little fast solution how to make rotation of text over its center before rendering it - tell me, pleeease.
For now I have:
#...
cr.move_to(*text_center)
myX, myY = text_center[0] - (width / 2), text_center[1] + (height / 2)
cr.save()
cr.translate(myX, myY)
cr.rotate(radians(text_angle))
cr.show_text(letter)
cr.restore()
#...
But my letter isn't rotating around itself. It's just like falling down to the right side :(I know that my code isn't right. Maybe I miss transformation but I don't know how to make it right.
UPDATE: Unfortunately, text are not affected by translations, so
cr.translate(10000, 10000)
cr.rotate(radians(15))
cr.show_text("hello")
will be exactly the same as
cr.rotate(radians(15))
cr.show_text("hello")
And I don't know how to make text rotation over its center without making new surface or something (like new layer in graphic processor) :(
At least on the version of cairo available on my machine (1.8.8), the following approach works for me:
def text(ctx, string, pos, theta = 0.0, face = 'Georgia', font_size = 18):
ctx.save()
# build up an appropriate font
ctx.select_font_face(face , cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
ctx.set_font_size(font_size)
fascent, fdescent, fheight, fxadvance, fyadvance = ctx.font_extents()
x_off, y_off, tw, th = ctx.text_extents(string)[:4]
nx = -tw/2.0
ny = fheight/2
ctx.translate(pos[0], pos[1])
ctx.rotate(theta)
ctx.translate(nx, ny)
ctx.move_to(0,0)
ctx.show_text(string)
ctx.restore()
Which can be used in the following way:
width = 500
height = 500
surface = cairo.ImageSurface(cairo.FORMAT_RGB24, width, height)
ctx = cairo.Context(surface)
ctx.set_source_rgb(1,1,1)
rect(ctx, (0,0), (width, height), stroke=False)
ctx.set_source_rgb(0,0,0)
for i in xrange(5):
for j in xrange(5):
x = 100 * i + 20
y = 100 * j + 20
theta = math.pi*0.25*(5*i+j)
text(ctx, 'hello world', (x, y), theta, font_size=15)
surface.write_to_png('text-demo.png')
这篇关于在pycairo中围绕其中心旋转文本的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！