openvg：探索OpenVG的工具

# Testbed for exploring OpenVG on the Raspberry Pi. <a href="http://www.flickr.com/photos/ajstarks/7811750326/" title="rotext by ajstarks, on Flickr"><img src="http://farm8.staticflickr.com/7249/7811750326_614ea891ae.jpg" width="500" height="281" alt="rotext"></a> ## First program Here is the graphics equivalent of "hello, world" // first OpenVG program // Anthony Starks (ajstarks@gmail.com) #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include "VG/openvg.h" #include "VG/vgu.h" #include "fontinfo.h" #include "shapes.h" int main() { int width, height; char s[3]; init(&width, &height); // Graphics initialization Start(width, height); // Start the picture Background(0, 0, 0); // Black background Fill(44, 77, 232, 1); // Big blue marble Circle(width / 2, 0, width); // The "world" Fill(255, 255, 255, 1); // White text TextMid(width / 2, height / 2, "hello, world", SerifTypeface, width / 10); // Greetings End(); // End the picture fgets(s, 2, stdin); // look at the pic, end with [RETURN] finish(); // Graphics cleanup exit(0); } <a href="http://www.flickr.com/photos/ajstarks/7828969180/" title="hellovg by ajstarks, on Flickr"><img src="http://farm9.staticflickr.com/8436/7828969180_b73db3bf19.jpg" width="500" height="281" alt="hellovg"></a> ## API <a href="http://www.flickr.com/photos/ajstarks/7717370238/" title="OpenVG refcard by ajstarks, on Flickr"><img src="http://farm8.staticflickr.com/7256/7717370238_1d632cb179.jpg" width="500" height="281" alt="OpenVG refcard"></a> Coordinates are VGfloat values, with the origin at the lower left, with x increasing to the right, and y increasing up. OpenVG specifies colors as a VGfloat array containing red, green, blue, alpha values ranging from 0.0 to 1.0, but typically colors are specified as RGBA (0-255 for RGB, A from 0.0 to 1.0) ### Window (canvas) functions void WindowClear() WindowClear clears the window to previously set background colour void AreaClear(unsigned int x, unsigned int y, unsigned int w, unsigned int h) AreaClear clears a given rectangle in window coordinates void WindowOpacity(unsigned int a) WindowOpacity sets the window opacity void WindowPosition(int x, int y) WindowPosition moves the window to given position ### Setup and shutdown void init(int *w, int *h) Initialize the graphics: width and height of the canvas are returned. This should begin every program. void initWindowSize(int x, int y, unsigned int w, unsigned int h) Initialize with specific dimensions void finish() Shutdown the graphics. This should end every program. void Start(int width, int height) Begin the picture, clear the screen with a default white, set the stroke and fill to black. void End() End the picture, rendering to the screen. void SaveEnd(char *filename) End the picture, rendering to the screen, save the raster to the named file as 4-byte RGBA words, with a stride of width*4 bytes. The program raw2png converts the "raw" raster to png. void saveterm(), restoreterm(), rawterm() Terminal settings, save current settings, restore settings, put the terminal in raw mode. ### Attributes void setfill(float color[4]) Set the fill color void Background(unsigned int r, unsigned int g, unsigned int b) Fill the screen with the background color defined from RGB values. void BackgroundRGB(unsigned int r, unsigned int g, unsigned int b, VGfloat a) clears the screen to a background color with alpha void StrokeWidth(float width) Set the stroke width. void RGBA(unsigned int r, unsigned int g, unsigned int b, VGfloat a, VGfloat color[4]) fill a color vector from RGBA values. void RGB(unsigned int r, unsigned int g, unsigned int b, VGfloat color[4]) fill a color vector from RGB values. void Stroke(unsigned int r, unsigned int g, unsigned int b, VGfloat a) Set the Stroke color using RGBA values. void Fill(unsigned int r, unsigned int g, unsigned int b, VGfloat a) Set the Fill color using RGBA values. void FillLinearGradient(VGfloat x1, VGfloat y1, VGfloat x2, VGfloat y2, VGfloat *stops, int n) Set the fill to a linear gradient bounded by (x1, y1) and (x2, y2). using offsets and colors specified in n number of stops void FillRadialGradient(VGfloat cx, VGfloat cy, VGfloat fx VGfloat fy, VGfloat r, VGfloat *stops, int n) Set the fill to a radial gradient centered at (cx, cy) with radius r, and focal point at (fx, ry), using offsets and colors specified in n number of stops ### Shapes void Line(VGfloat x1, VGfloat y1, VGfloat x2, VGfloat y2) Draw a line between (x1, y1) and (x2, y2). void Rect(VGfloat x, VGfloat y, VGfloat w, VGfloat h) Draw a rectangle with its origin (lower left) at (x,y), and size is (width,height). void RectOutline(VGfloat x, VGfloat y, VGfloat w, VGfloat h) Outlined version void Roundrect(VGfloat x, VGfloat y, VGfloat w, VGfloat h, VGfloat rw, VGfloat rh) Draw a rounded rectangle with its origin (lower left) at (x,y), and size is (width,height). The width and height of the corners are specified with (rw,rh). void RoundrectOutline(VGfloat x, VGfloat y, VGfloat w, VGfloat h, VGfloat rw, VGfloat rh) Outlined version void Polygon(VGfloat *x, VGfloat *y, VGint n) Draw a polygon using the coordinates in arrays pointed to by x and y. The number of coordinates is n. void Polyline(VGfloat *x, VGfloat *y, VGint n) Draw a polyline using the coordinates in arrays pointed to by x and y. The number of coordinates is n. void Circle(VGfloat x, VGfloat y, VGfloat d) Draw a circle centered at (x,y) with diameter d. void CircleOutline(VGfloat x, VGfloat y, VGfloat r) Outlined version void Ellipse(VGfloat x, VGfloat y, VGfloat w, VGfloat h) Draw an ellipse centered at (x,y) with radii (w, h). void EllipseOutline(VGfloat x, VGfloat y, VGfloat w, VGfloat h) Outlined version void Qbezier(VGfloat sx, VGfloat sy, VGfloat cx, VGfloat cy, VGfloat ex, VGfloat ey) Draw a quadratic bezier curve beginning at (sx, sy), using control points at (cx, cy), ending at (ex, ey). void QbezierOutline(VGfloat sx, VGfloat sy, VGfloat cx, VGfloat cy, VGfloat ex, VGfloat ey) Outlined version void Cbezier(VGfloat sx, VGfloat sy, VGfloat cx, VGfloat cy, VGfloat px, VGfloat py, VGfloat ex, VGfloat ey) Draw a cubic bezier curve beginning at (sx, sy), using control points at (cx, cy) and (px, py), ending at (ex, ey). void CbezierOutline(VGfloat sx, VGfloat sy, VGfloat cx, VGfloat cy, VGfloat px, VGfloat py, VGfloat ex, VGfloat ey) Outlined version void Arc(VGfloat x, VGfloat y, VGfloat w, VGfloat h, VGfloat sa, VGfloat aext) Draw an elliptical arc centered at (x, y), with width and height at (w, h). Start angle (degrees) is sa, angle extent is aext. void ArcOutline(VGfloat x, VGfloat y, VGfloat w, VGfloat h, VGfloat sa, VGfloat aext) Outlined version ### Text and Images void Text(VGfloat x, VGfloat y, char* s, Fontinfo f, int pointsize) Draw a the text srtring (s) at location (x,y), using pointsize. void TextMid(VGfloat x, VGfloat y, char* s, Fontinfo f, int pointsize) Draw a the text srtring (s) at centered at location (x,y), using pointsize. void TextEnd(VGfloat x, VGfloat y, char* s, Fontinfo f, int pointsize) Draw a the text srtring (s) at with its lend aligned to location (x,y), using pointsize VGfloat TextWidth(char *s, Fontinfo f, int pointsize) Return the width of text VGfloat TextHeight(Fontinfo f, int pointsize) Return a font's height TextDepth(Fontinfo f, int pointsize) Return a font's distance beyond the baseline. void Image(VGfloat x, VGfloat y, int w, int h, char * filename) place a JPEG image with dimensions (w,h) at (x,y). ### Transformations void Translate(VGfloat x, VGfloat y) Translate the coordinate system to (x,y). void Rotate(VGfloat r) Rotate the coordinate system around angle r (degrees). void Scale(VGfloat x, VGfloat y) Scale by x,y. void Shear(VGfloat x, VGfloat y) Shear by the angles x,y. ## Clipping void C