C++ 使用 Skia 绘图

索引

前言
Skia 准备
- 项目实践——Hello World

前言

Skia 准备

下载Skia，国内skia编译门槛搞，所以此处直接使用Jetbrain在GitHub上的库（本文使用m93）

Releases · JetBrains/skia-build (github.com)
分别下载Debug和Release两个版本，放至一个目录下（建议目录）
```
Skia
| Debug
| | Debug压缩包解压
| Release
| | Release压缩包解压
```

项目实践——【Hello World】

创建项目并设置项目属性

创建控制台项目，建议使用预编译头。此处开始笔者将指引您如何配置项目属性。首先，右键单击项目→属性(Properties)→C/C++→常规(General)→附加包含目录(Additional Include Directories)，按照上一步建议的目录，分别对应Debug和Release填入。

注意：Debug和Release一定要区分
链接静态库

因为是初学，暂时只用得到skia.lib

同样的，右键单击项目→属性(Properties)→链接器(Linker)→常规(General)→附加库目录(Additional Library Directories)，将Debug和Release中静态库的目录分别对应输入。

执行完上述步骤，再转到链接器(Linker)→输入(Input)→附加依赖项(Additional Dependencies)
引入头文件

我们已经配置好了Debug和Release环境，但是实际还需要一些东西。

在预编译头末尾添加以下代码：
```
// Skia Dependencies
#include <d3d12.h>
#pragma comment(lib, "D3D12.lib")
#include <d3dcompiler.h>
#pragma comment(lib, "d3dcompiler.lib")
#pragma comment(lib, "Opengl32.lib")
#ifdef _DEBUG
#include <dxgi1_3.h>
#pragma comment(lib, "DXGI.lib")
#endif // _DEBUG
```
解释一下，这些东西是Skia的依赖项，所以一定要加上，因为有用到DXGIGetDebugInterface1（具体是什么我也不知道）但这是DXGI.lib的一个函数，并且Debug环境下不可缺少，所以用预编译命令设置在Debug模式下链接DXGI.lib。这样就可以通过编译。

注意：如果要引用Skia的头文件，须在上述代码片段前引入；如果预编译头文件中有Windows.h，请将其移至上述代码后，否则会出现大量错误

编写代码

预编译头（笔者是pch.h文件）

// pch.h: This is a precompiled header file.
// Files listed below are compiled only once, improving build performance for future builds.
// This also affects IntelliSense performance, including code completion and many code browsing features.
// However, files listed here are ALL re-compiled if any one of them is updated between builds.
// Do not add files here that you will be updating frequently as this negates the performance advantage.

#ifndef PCH_H
#define PCH_H

// add headers that you want to pre-compile here

#endif //PCH_H

// Skia
#include <include/core/SkCanvas.h>
#include <include/core/SkPaint.h>
#include <include/core/SkPath.h>
#include <include/core/SkShader.h>
#include <src/utils/SkShaderUtils.h>
#include <include/core/SkTypeface.h>
#include <include/core/SkTypes.h>
#include <include/core/SkFont.h>
#include <include/core/SkFontStyle.h>
#include <include/core/SkFontTypes.h>
#include <include/core/SkSurface.h>
#include <include/codec/SkCodec.h>
#include <include/core/SkPngChunkReader.h>
#include <src/core/SkShaderCodeDictionary.h>
#include <src/core/SkBitmapDevice.h>

// Skia Depency
#include <d3d12.h>
#pragma comment(lib, "D3D12.lib")
#include <d3dcompiler.h>
#pragma comment(lib, "d3dcompiler.lib")
//#include <wingdi.h>
#pragma comment(lib, "Opengl32.lib")
#ifdef _DEBUG
#include <dxgi1_3.h>
#pragma comment(lib, "DXGI.lib")
#endif // _DEBUG

#include <Windows.h>

主程序代码（main.cpp）

#include "pch.h"
#include <iostream>

int main()
{
	SkBitmap bitmap;
	SkImageInfo imageInfo = SkImageInfo::Make(480, 320, kBGRA_8888_SkColorType, kPremul_SkAlphaType);
	bitmap.allocPixels(imageInfo, imageInfo.minRowBytes());
	SkCanvas canvas(bitmap);
	SkPaint paint;
	canvas.clear(0x00000000);
	paint.setColor(SK_ColorBLACK);

	SkRect rect;
	rect.fBottom = 100;
	rect.fTop = 10;
	rect.fLeft = 10;
	rect.fRight = 100;
	SkFont font;
	font.setSize(64);
	font.setTypeface(SkTypeface::MakeFromName("Microsoft YaHei", SkFontStyle::Normal()));
	canvas.drawSimpleText("Hello World", sizeof("Hello World") - 1, SkTextEncoding::kUTF8, 0, 64, font, paint);
	SkFILEWStream stream("D:\\test.png");
	SkEncodeImage(&stream, bitmap, SkEncodedImageFormat::kPNG, 100);
	return 0;
}