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* Copyright 2015 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "../include/core/SkCanvas.h"
#include "../include/core/SkData.h"
#include "../include/core/SkSurface.h"
#include "../include/effects/SkGradientShader.h"
#include "../include/gpu/GrContext.h"
// These headers are just handy for writing this example file. Nothing Skia specific.
#include <cstdlib>
#include <ctime>
#include <fstream>
#include <iostream>
#include <memory>
// These setup_gl_context() are not meant to represent good form.
// They are just quick hacks to get us going.
#if defined(__APPLE__)
#include <OpenGL/OpenGL.h>
static bool setup_gl_context() {
CGLPixelFormatAttribute attributes[] = { (CGLPixelFormatAttribute)0 };
CGLPixelFormatObj format;
GLint npix;
CGLChoosePixelFormat(attributes, &format, &npix);
CGLContextObj context;
CGLCreateContext(format, nullptr, &context);
return true;
static bool setup_gl_context() {
return false;
// Most pointers returned by Skia are derived from SkRefCnt,
// meaning we need to call ->unref() on them when done rather than delete them.
template <typename T> std::shared_ptr<T> adopt(T* ptr) {
return std::shared_ptr<T>(ptr, [](T* p) { p->unref(); });
static std::shared_ptr<SkSurface> create_raster_surface(int w, int h) {
std::cout << "Using raster surface" << std::endl;
return adopt(SkSurface::NewRasterN32Premul(w, h));
static std::shared_ptr<SkSurface> create_opengl_surface(int w, int h) {
std::cout << "Using opengl surface" << std::endl;
std::shared_ptr<GrContext> grContext = adopt(GrContext::Create(kOpenGL_GrBackend, 0));
return adopt(SkSurface::NewRenderTarget(grContext.get(),
int main(int, char**) {
bool gl_ok = setup_gl_context();
std::shared_ptr<SkSurface> surface = (gl_ok && rand() % 2) ? create_opengl_surface(320, 240)
: create_raster_surface(320, 240);
// Create a left-to-right green-to-purple gradient shader.
SkPoint pts[] = { {0,0}, {320,240} };
SkColor colors[] = { 0xFF00FF00, 0xFFFF00FF };
std::shared_ptr<SkShader> shader = adopt(
SkGradientShader::CreateLinear(pts, colors, nullptr, 2, SkShader::kRepeat_TileMode));
// Our text will draw with this paint: size 24, antialiased, with the shader.
SkPaint paint;
// Draw to the surface via its SkCanvas.
SkCanvas* canvas = surface->getCanvas(); // We don't manage this pointer's lifetime.
static const char* msg = "Hello world!";
canvas->drawText(msg, strlen(msg), 90,120, paint);
// Grab a snapshot of the surface as an immutable SkImage.
std::shared_ptr<SkImage> image = adopt(surface->newImageSnapshot());
// Encode that image as a .png into a blob in memory.
std::shared_ptr<SkData> png = adopt(image->encode(SkImageEncoder::kPNG_Type, 100));
// This code is no longer Skia-specific. We just dump the .png to disk. Any way works.
static const char* path = "example.png";
std::ofstream(path, std::ios::out | std::ios::binary)
.write((const char*)png->data(), png->size());
std::cout << "Wrote " << path << std::endl;
return 0;