| <?xml version="1.0" ?> |
| <svgslides |
| xmlns="http://www.svgslides.org/svgslides0.1" |
| xmlns:svg="http://www.w3.org/2000/svg" |
| xmlns:xlink="http://www.w3.org/1999/xlink" |
| > |
| |
| <slides theme="cairo" |
| presentation="Drawing with cairo" |
| presentation-subtitle="drawing with cairo" |
| URL="http://cairographics.org" |
| bullet="bullet"> |
| |
| <slide title="Tutorial preparation" variant="blank" bullet=""> |
| <lc></lc> |
| <lc align="center">http://cairographics.org/tutorial</lc> |
| <lc></lc> |
| <li>wget http://cairographics.org/cairo-tutorial.tar.gz</li> |
| <li>tar xzf cairo-tutorial.tar.gz</li> |
| <li>cd cairo-tutorial</li> |
| <li>make</li> |
| <li>cat README</li> |
| <lc></lc> |
| <lc align="center">IRC: irc.freenode.net #cairo</lc> |
| </slide> |
| |
| <slide variant="title"> |
| <lc>Carl Worth</lc> |
| <lc>Red Hat, Inc.</lc> |
| <lc></lc> |
| <lc>linux.conf.au</lc> |
| <lc>2006-01-26</lc> |
| <lc>http://cairographics.org</lc> |
| </slide> |
| |
| <slide title="Ugly graphics" variant="separator"> |
| <lc align="left">Jaggies</lc> |
| <lc align="center">Fuzzies</lc> |
| <lc align="right">Fireworks</lc> |
| </slide> |
| |
| <slide title="Jaggies"> |
| <img src="jaggies.svg"/> |
| </slide> |
| |
| <slide title="Fuzzies"> |
| <img src="fuzzies.svg"/> |
| </slide> |
| |
| <slide title="Fireworks"> |
| </slide> |
| |
| <slide title="What you can do about it"> |
| <li>Let application authors know there are options</li> |
| <li>Learn to use cairo—patch the applications</li> |
| <li>Write your own cairo-using applications</li> |
| </slide> |
| |
| <slide title="Getting started" variant="separator"> |
| <lc align="center">Various shell cairo programs</lc> |
| </slide> |
| |
| <slide title="Minimal cairo-xlib program" variant="code"> |
| <lc>#include <cairo.h></lc> |
| <lc>#include <cairo-xlib.h></lc> |
| <lc>int main (void) {</lc> |
| <lc> Display *dpy = XOpenDisplay (0);</lc> |
| <lc> Window w = XCreateSimpleWindow (dpy,RootWindow (dpy, 0),</lc> |
| <lc> 0, 0, WIDTH, HEIGHT, 0, 0, WhitePixel (dpy, 0));</lc> |
| <lc> cairo_surface_t *surface = cairo_xlib_surface_create (dpy, w,</lc> |
| <lc> DefaultVisual (dpy, DefaultScreen (dpy)),</lc> |
| <lc> WIDTH, HEIGHT);</lc> |
| <lc> XEvent ev;</lc> |
| <lc> XSelectInput (dpy, w, ExposureMask);</lc> |
| <lc> XMapWindow (dpy, w);</lc> |
| <lc> while (XNextEvent (dpy, &ev) == 0)</lc> |
| <lc> if (ev.type == Expose && !ev.xexpose.count) {</lc> |
| <lc> cairo_t *cr = cairo_create (surface);</lc> |
| <lc> draw (cr);</lc> |
| <lc> cairo_destroy (cr);</lc> |
| <lc> }</lc> |
| <lc>}</lc> |
| </slide> |
| |
| <slide title="Minimal cairo-gtk program" variant="code"> |
| <lc>#include <gtk/gtk.h></lc> |
| <lc>static gboolean</lc> |
| <lc>handle_expose (GtkWidget *widget, GdkEventExpose *event, gpointer data) {</lc> |
| <lc> cairo_t *cr = gdk_cairo_create (widget->window);</lc> |
| <lc> draw (cr);</lc> |
| <lc> cairo_destroy (cr);</lc> |
| <lc> return FALSE;</lc> |
| <lc>}</lc> |
| <lc>int main (int argc, char **argv) {</lc> |
| <lc> GtkWidget *window, *drawing_area;</lc> |
| <lc> gtk_init (&argc, &argv);</lc> |
| <lc> window = gtk_window_new (GTK_WINDOW_TOPLEVEL);</lc> |
| <lc> gtk_window_set_default_size (GTK_WINDOW (window), WIDTH, HEIGHT);</lc> |
| <lc> drawing_area = gtk_drawing_area_new ();</lc> |
| <lc> gtk_container_add (GTK_CONTAINER (window), drawing_area);</lc> |
| <lc> g_signal_connect (drawing_area, "expose-event",</lc> |
| <lc> G_CALLBACK (handle_expose), NULL);</lc> |
| <lc> gtk_widget_show_all (window); gtk_main ();</lc> |
| <lc>}</lc> |
| </slide> |
| |
| <slide title="Minimal cairo-png program" variant="code"> |
| <lc>#include <cairo.h></lc> |
| <lc></lc> |
| <lc>int main (void)</lc> |
| <lc>{</lc> |
| <lc> cairo_surface_t *surface;</lc> |
| <lc> cairo_t *cr;</lc> |
| <lc></lc> |
| <lc> surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,</lc> |
| <lc> WIDTH, HEIGHT);</lc> |
| <lc> cr = cairo_create (surface);</lc> |
| <lc> draw (cr);</lc> |
| <lc> cairo_surface_write_to_png (surface, "foo.png");</lc> |
| <lc></lc> |
| <lc> cairo_surface_destroy (surface);</lc> |
| <lc> cairo_destroy (cr);</lc> |
| <lc></lc> |
| <lc> return 0;</lc> |
| <lc>}</lc> |
| </slide> |
| |
| <slide title="Minimal cairo-pdf program" variant="code"> |
| <lc>#include <cairo.h></lc> |
| <lc>#include <cairo-pdf.h></lc> |
| <lc>int main (void)</lc> |
| <lc>{</lc> |
| <lc> cairo_surface_t *surface;</lc> |
| <lc> cairo_t *cr;</lc> |
| <lc></lc> |
| <lc> surface = cairo_pdf_surface_create ("foo.pdf", WIDTH, HEIGHT);</lc> |
| <lc> </lc> |
| <lc> cr = cairo_create (surface);</lc> |
| <lc> draw (cr);</lc> |
| <lc> cairo_show_page (cr);</lc> |
| <lc></lc> |
| <lc> cairo_surface_destroy (surface);</lc> |
| <lc> cairo_destroy (cr);</lc> |
| <lc></lc> |
| <lc> return 0;</lc> |
| <lc>}</lc> |
| </slide> |
| |
| <slide title="Minimal pycairo-gtk shell" variant="code"> |
| <lc>#!/usr/bin/env python</lc> |
| <lc>import gtk</lc> |
| <lc>import cairo</lc> |
| <lc></lc> |
| <lc>def expose (widget, event):</lc> |
| <lc> cr = widget.window.cairo_create ()</lc> |
| <lc> draw (cr)</lc> |
| <lc> </lc> |
| <lc>win = gtk.Window ()</lc> |
| <lc>win.connect ('destroy', gtk.main_quit)</lc> |
| <lc>win.set_default_size(WIDTH, HEIGHT)</lc> |
| <lc>drawingarea = gtk.DrawingArea ()</lc> |
| <lc>win.add (drawingarea)</lc> |
| <lc>drawingarea.connect ('expose_event', expose)</lc> |
| <lc>win.show_all ()</lc> |
| <lc>gtk.main ()</lc> |
| </slide> |
| |
| <slide title="Minimal pycairo-png shell" variant="code"> |
| <lc>#!/usr/bin/env python</lc> |
| <lc>import cairo</lc> |
| <lc></lc> |
| <lc>surface = cairo.ImageSurface (cairo.FORMAT_ARGB32, WIDTH, HEIGHT)</lc> |
| <lc>cr = cairo.Context (surface)</lc> |
| <lc></lc> |
| <lc>draw (cr)</lc> |
| <lc></lc> |
| <lc>surface.write_to_png ('foo.png')</lc> |
| </slide> |
| |
| <slide title="Minimal nickle program" variant="code"> |
| <lc>autoimport Cairo;</lc> |
| <lc></lc> |
| <lc>cairo_t cr = new (WIDTH, HEIGHT);</lc> |
| <lc>draw (cr);</lc> |
| </slide> |
| |
| <slide title="Available bindings:" variant="large-content"> |
| <li>C++ (cairomm)</li> |
| <li>Haskell (hscairo)</li> |
| <li>Java (CairoJava, cairo-java)</li> |
| <li>Common Lisp (cl-cairo)</li> |
| <li>Nickle (cairo-5c)</li> |
| <li>Objective Caml (cairo-ocaml)</li> |
| <li>perl (cairo-perl)</li> |
| <li>python (pycairo)</li> |
| <li>ruby (rcairo)</li> |
| <li>squeak (cairo-squeak)</li> |
| </slide> |
| |
| <slide title="Following along" > |
| <lc></lc> |
| <lc align="center">http://cairographics.org/tutorial</lc> |
| <lc align="center">http://cairographics.org/cairo-tutorial.tar.gz</lc> |
| <li>tar xzf cairo-tutorial.tar.gz</li> |
| <li>cd cairo-tutorial</li> |
| <li>make</li> |
| <li>cat README</li> |
| <lc align="center">IRC: irc.freenode.net #cairo</lc> |
| </slide> |
| |
| <slide title="Cairo's rendering model"> |
| <g> |
| <image x="0" y="0" xlink:href="rendering-model.png" width="800" height="500" /> |
| </g> |
| </slide> |
| |
| <slide title="Let's start drawing" variant="separator"> |
| <lc align="center">Here comes the fun part</lc> |
| </slide> |
| |
| <slide title="API Overview" variant="large-content"> |
| <ul> |
| <li>Paths</li> |
| <ul> |
| <li>construction</li> |
| <li>filling, stroking</li> |
| </ul> |
| <li>Images</li> |
| <ul> |
| <li>loading from disk</li> |
| <li>using as source</li> |
| <li>transforming/filtering</li> |
| </ul> |
| <li>Text</li> |
| <ul> |
| <li>“Toy” API</li> |
| <li>“Full” API</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="Drawing functions" variant="large-content"> |
| <ul> |
| <li>Paths</li> |
| <ul> |
| <li>cairo_stroke</li> |
| <li>cairo_fill</li> |
| </ul> |
| <li>Images</li> |
| <ul> |
| <li>cairo_paint</li> |
| <li>cairo_mask</li> |
| <li>cairo_paint_with_alpha</li> |
| </ul> |
| <li>Text</li> |
| <ul> |
| <li>cairo_show_text (“toy”)</li> |
| <li>cairo_show_glyphs (“full”)</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="Basic path building"> |
| <ul> |
| <li>Paths consist of lines and splines:</li> |
| <ul> |
| <li>cairo_move_to</li> |
| <lc> start new sub path, set current point</lc> |
| <li>cairo_line_to</li> |
| <lc> add line segment to path</lc> |
| <li>cairo_curve_to</li> |
| <lc> add Bézier spline to path</lc> |
| <li>cairo_close_path</li> |
| <lc> add line segment to last move_to point</lc> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="Stroking paths"> |
| <ul> |
| <li>cairo_stroke</li> |
| <ul> |
| <li>Paints the path itself as stroked by a pen</li> |
| <li>Controlled by various stroke parameters:</li> |
| <ul> |
| <li>cairo_set_line_width</li> |
| <li>cairo_set_line_cap</li> |
| <li>cairo_set_line_join</li> |
| <li>cairo_set_miter_limit</li> |
| <li>cairo_set_dash</li> |
| </ul> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="cairo_stroke example"> |
| </slide> |
| |
| <slide title="cairo_set_line_width"> |
| </slide> |
| |
| <slide title="cairo_set_line_cap example"> |
| <ul> |
| <li>CAIRO_LINE_CAP_BUTT</li> |
| <li>CAIRO_LINE_CAP_ROUND</li> |
| <li>CAIRO_LINE_CAP_SQUARE</li> |
| </ul> |
| </slide> |
| |
| <slide title="cairo_set_line_join example"> |
| <ul> |
| <li>CAIRO_LINE_JOIN_BEVEL</li> |
| <li>CAIRO_LINE_JOIN_ROUND</li> |
| <li>CAIRO_LINE_JOIN_MITER</li> |
| </ul> |
| </slide> |
| |
| <slide title="cairo_close_path example"> |
| <li>Adds a line segment (if necessary) to the</li> |
| <lc>start of the path</lc> |
| <li>Draws a join from that line to the first</li> |
| <lc>element of the path</lc> |
| </slide> |
| |
| <slide title="cairo_set_dash example"> |
| </slide> |
| |
| <slide title="cairo_fill"> |
| <ul> |
| <li>Paints the “inside” of the path</li> |
| <li>Two different ways to determine inside-ness</li> |
| <ul> |
| <li>cairo_set_fill_rule:</li> |
| <lc> CAIRO_FILL_RULE_WINDING</lc> |
| <lc> CAIRO_FILL_RULE_EVEN_ODD</lc> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="cairo_fill example"> |
| </slide> |
| |
| <slide title="cairo_set_fill_rule"> |
| <li>To test a point for inside-ness, imagine a ray</li> |
| <lc>from the point and extending to infinity</lc> |
| <lc>(any direction) and examine path crossings</lc> |
| <li>EVEN_ODD counts crossings and fills when odd</li> |
| <li>WINDING counts up/down for left/right crossings</li> |
| <lc>and fills when the final number is not zero</lc> |
| </slide> |
| |
| <slide title="Fill rule example"> |
| </slide> |
| |
| <slide title="Something besides black?"> |
| <li>All drawing occurs with the source pattern</li> |
| <li>Uniform-color sources can be set</li> |
| <lc>with or without alpha:</lc> |
| <ul> |
| <li>cairo_set_source_rgb</li> |
| <li>cairo_set_source_rgba</li> |
| </ul> |
| </slide> |
| |
| <slide title="cairo_set_source example"> |
| </slide> |
| |
| <slide title="Fill and stroke the same path"> |
| <li>cairo_stroke and cairo_fill consume the path</li> |
| <li>Variants are available to preserve the path:</li> |
| <ul> |
| <li>cairo_stroke_preserve</li> |
| <li>cairo_fill_preserve</li> |
| </ul> |
| <li>This is a variation from PostScript and PDF</li> |
| <ul> |
| <li>The cairo approach differs in different ways</li> |
| <li>We think this way is better (of course)</li> |
| </ul> |
| </slide> |
| |
| <slide title="Fill and stroke example"> |
| </slide> |
| |
| <slide title="More path building"> |
| <ul> |
| <li>cairo_rectangle</li> |
| <li>cairo_arc</li> |
| <li>cairo_text_path</li> |
| <li>cairo_glyph_path</li> |
| <li>Relative-coordinate variants:</li> |
| <ul> |
| <li>cairo_rel_move_to</li> |
| <li>cairo_rel_line_to</li> |
| <li>cairo_rel_curve_to</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="cairo_arc example"> |
| </slide> |
| |
| <slide title="Outline text"> |
| </slide> |
| |
| <slide title="Affine Transformations"> |
| <ul> |
| <li>Single matrix combines rotation, translation,</li> |
| <lc>scale and shear</lc> |
| <li>Non-projective transformations</li> |
| <ul> |
| <li>Pen doesn't change shape along the stroke</li> |
| </ul> |
| <li>Transformations are cumulative</li> |
| <ul> |
| <li>translate, scale != scale, translate</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="Affine Transform Example"> |
| </slide> |
| |
| <slide title="Save/Restore Graphics States"> |
| <ul> |
| <li>cairo_save and cairo_restore</li> |
| <li>Very useful for bracketing function bodies</li> |
| <li>Eliminates graphics state side effects</li> |
| <lc></lc> |
| <li>NOTE: Path is not part of graphics state</li> |
| <ul> |
| <li>Path is not affected by cairo_save/restore</li> |
| <li>Useful for path-generating functions</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="Clipping"> |
| <li>cairo_clip</li> |
| <li>Intersects path with current clip to further</li> |
| <lc>restrict drawing</lc> |
| <li>Pixel-aligned clipping is much faster</li> |
| <li>cairo_clip_preserve is available as well</li> |
| </slide> |
| |
| <slide title="Other source patterns"> |
| <ul> |
| <li>Surface patterns</li> |
| <ul> |
| <li>Image from disk</li> |
| <li>Results of cairo drawing</li> |
| </ul> |
| <li>Gradient patterns</li> |
| <ul> |
| <li>linear gradients</li> |
| <li>radial gradients</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="Loading an image file"> |
| </slide> |
| |
| <slide title="Painting an image"> |
| </slide> |
| |
| <slide title="Pattern transformation"> |
| </slide> |
| |
| <slide title="Pattern filtering"> |
| </slide> |
| |
| <slide title="Linear gradient example"> |
| </slide> |
| |
| <slide title="Radial gradient example"> |
| </slide> |
| |
| <slide title="Text"> |
| <ul> |
| <li>“Toy” API:</li> |
| <ul> |
| <li>Useful for demos like we are writing today</li> |
| <li>No real layout—not useful for the majority</li> |
| <lc>of writing systems in the world</lc> |
| </ul> |
| <li>“Full” API:</li> |
| <ul> |
| <li>User must do OS-dependent font selection</li> |
| <li>User must access font glyph IDs directly</li> |
| <li>User must do all text layout</li> |
| </ul> |
| </ul> |
| </slide> |
| |
| <slide title="“Toy” text API"/> |
| <ul> |
| <li>Simple font selection</li> |
| <ul> |
| <li>family, weight, slant</li> |
| <li>OS independent</li> |
| <li>No font listing support</li> |
| </ul> |
| <li>UTF-8 text drawing and extents functions</li> |
| <li>Still supports full font transformations</li> |
| </ul> |
| |
| <slide title="“Toy” text example"> |
| </slide> |
| |
| <slide title="“Real” text example"> |
| <li>Just use pango</li> |
| </slide> |
| |
| <slide title="Error handling in C"> |
| <li>C has no exceptions</li> |
| <li>Checking each return is tedious</li> |
| <li>C programmers rarely bother</li> |
| <li>Lots of broken programs result</li> |
| </slide> |
| |
| <slide title="Cairo error handling"> |
| <li>Cairo stores status value when error occurs</li> |
| <li>API “shuts down” when an error occurs</li> |
| <li>All cairo functions are benign</li> |
| <lc>(and well defined) after any error.</lc> |
| <li>cairo_status can be called when convenient</li> |
| <li>Error status values propagate across objects</li> |
| </slide> |
| |
| <slide title="Cairo error example"> |
| </slide> |
| |
| </slides> |
| </svgslides> |
