1 /*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "../include/core/SkCanvas.h"
9 #include "../include/core/SkData.h"
10 #include "../include/core/SkSurface.h"
11 #include "../include/effects/SkGradientShader.h"
12 #include "../include/gpu/GrContext.h"
13
14 // These headers are just handy for writing this example file. Nothing Skia specific.
15 #include <cstdlib>
16 #include <ctime>
17 #include <fstream>
18 #include <iostream>
19 #include <memory>
20
21 // These setup_gl_context() are not meant to represent good form.
22 // They are just quick hacks to get us going.
23 #if defined(__APPLE__)
24 #include <OpenGL/OpenGL.h>
setup_gl_context()25 static bool setup_gl_context() {
26 CGLPixelFormatAttribute attributes[] = { (CGLPixelFormatAttribute)0 };
27 CGLPixelFormatObj format;
28 GLint npix;
29 CGLChoosePixelFormat(attributes, &format, &npix);
30 CGLContextObj context;
31 CGLCreateContext(format, nullptr, &context);
32 CGLSetCurrentContext(context);
33 CGLReleasePixelFormat(format);
34 return true;
35 }
36 #else
setup_gl_context()37 static bool setup_gl_context() {
38 return false;
39 }
40 #endif
41
42 // Most pointers returned by Skia are derived from SkRefCnt,
43 // meaning we need to call ->unref() on them when done rather than delete them.
adopt(T * ptr)44 template <typename T> std::shared_ptr<T> adopt(T* ptr) {
45 return std::shared_ptr<T>(ptr, [](T* p) { p->unref(); });
46 }
47
create_raster_surface(int w,int h)48 static std::shared_ptr<SkSurface> create_raster_surface(int w, int h) {
49 std::cout << "Using raster surface" << std::endl;
50 return adopt(SkSurface::NewRasterN32Premul(w, h));
51 }
52
create_opengl_surface(int w,int h)53 static std::shared_ptr<SkSurface> create_opengl_surface(int w, int h) {
54 std::cout << "Using opengl surface" << std::endl;
55 std::shared_ptr<GrContext> grContext = adopt(GrContext::Create(kOpenGL_GrBackend, 0));
56 return adopt(SkSurface::NewRenderTarget(grContext.get(),
57 SkBudgeted::kNo,
58 SkImageInfo::MakeN32Premul(w,h)));
59 }
60
main(int,char **)61 int main(int, char**) {
62 bool gl_ok = setup_gl_context();
63 srand(time(nullptr));
64 std::shared_ptr<SkSurface> surface = (gl_ok && rand() % 2) ? create_opengl_surface(320, 240)
65 : create_raster_surface(320, 240);
66
67 // Create a left-to-right green-to-purple gradient shader.
68 SkPoint pts[] = { {0,0}, {320,240} };
69 SkColor colors[] = { 0xFF00FF00, 0xFFFF00FF };
70 std::shared_ptr<SkShader> shader = adopt(
71 SkGradientShader::CreateLinear(pts, colors, nullptr, 2, SkShader::kRepeat_TileMode));
72
73 // Our text will draw with this paint: size 24, antialiased, with the shader.
74 SkPaint paint;
75 paint.setTextSize(24);
76 paint.setAntiAlias(true);
77 paint.setShader(shader.get());
78
79 // Draw to the surface via its SkCanvas.
80 SkCanvas* canvas = surface->getCanvas(); // We don't manage this pointer's lifetime.
81 static const char* msg = "Hello world!";
82 canvas->clear(SK_ColorWHITE);
83 canvas->drawText(msg, strlen(msg), 90,120, paint);
84
85 // Grab a snapshot of the surface as an immutable SkImage.
86 std::shared_ptr<SkImage> image = adopt(surface->newImageSnapshot());
87 // Encode that image as a .png into a blob in memory.
88 std::shared_ptr<SkData> png = adopt(image->encode(SkImageEncoder::kPNG_Type, 100));
89
90 // This code is no longer Skia-specific. We just dump the .png to disk. Any way works.
91 static const char* path = "example.png";
92 std::ofstream(path, std::ios::out | std::ios::binary)
93 .write((const char*)png->data(), png->size());
94 std::cout << "Wrote " << path << std::endl;
95
96 return 0;
97 }
98