ruby-****@sourc*****
ruby-****@sourc*****
2013年 3月 25日 (月) 18:34:36 JST
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REMOTE_ADDR = 70.49.48.128
REMOTE_HOST =
URL = http://ruby-gnome2.sourceforge.jp/hiki.cgi?tut-gtk2-dancr-rbcatut
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@@ -313,6 +313,15 @@
window.show_all
Gtk.main
+ :Scale
+ (12.3.1.2.1.A1){{br}}
+
+ This example introduces an unnecessary complication, that needs additional explanation, which in original Cairo tutorial, Michael defers until paragraph 12.3.4 ((<Working with Transforms|tut-gtk2-dancr-rbcatut#Working with Transforms>)) below. I found such treatment of this issue rather confusing for a beginner learning Cairo library basics. Namely, the transforms are too advanced for you to understand at this point, whereas, the scale method is far less complicated than a beginner might think after a introducing it too quickly without explaining what it really means.
+
+ Looking at the output of the above (12.3.1.2.1) example code does not reveal the important details. A much better results would be achieved, if the((*default scale*))were used. The default scale, namely is set as((*scale(1, 1).*)) However, this would require, that rectangle coordinates were given in pixels rather than in relative notation (i.e. as fractions), which calls for a short detour explaining these issues. This actually is exactly what we here are doing.
+
+ The most important thing here is understanding the parameters passed to the scale method:((*scale(sx, sy).*)) The((*sx*))and((*sy*)) parameters actually represents((*pixels*)). Namely,((*scale(1,1)*)) means that your working area will be measured in pixels. The size of 1 pixel depends on the device (display) you are using. Commonly one pixel is 1/75" = 0.0133". This means that if you use a 75dpi display, for instance 100 pixels will translate to 1.33" (3.378 cm). Now, if you set cairo context's scale to((*scale(2,2),*)) 100 pixels would translate to twice that, i.e. 2.66" (6.756 cm). Imagine using((*scale(100,100).*)) That would translate to 133" (337.8 cm). Unless you are very rich, I do not think, you will ever have a display capable of displaying such a large image!
+