前言
在上一篇理论文章中我们介绍了YUV到RGB之间转换的几种公式与一些优化算法，今天我们再来介绍一下RGB到YUV的转换，顺便使用Opengl ES做个实践，将一张RGB的图片通过Shader 的方式转换YUV格式图，然后保存到本地。
可能有的童鞋会问，YUV转RGB是为了渲染显示，那么RGB转YUV的应用场景是什么？在做视频编码的时候我们可以使用MediaCodec搭配Surface就可以完成，貌似也没有用到RGB转YUV的功能啊， 硬编码没有用到，那么软编码呢？一般我们做视频编码的时候都是硬编码优先，软编码兜底的原则，在遇到一些硬编码不可用的情况下可能就需要用到x264库进行软编码了，而此时RGB转YUV可能就派上用场啦。
RGB到YUV的转换公式
在前面 Opengl ES之YUV数据渲染 一文中我们介绍过YUV的几种兼容标准，下面我们看看RGB到YUV的转换公式：
RGB 转 BT.601 YUV
Y = 0.257R + 0.504G + 0.098B + 16
Cb = -0.148R - 0.291G + 0.439B + 128
Cr = 0.439R - 0.368G - 0.071B + 128RGB 转 BT.709 YUV
Y = 0.183R + 0.614G + 0.062B + 16
Cb = -0.101R - 0.339G + 0.439B + 128
Cr = 0.439R - 0.399G - 0.040B + 128或者也可以使用矩阵运算的方式进行转换，更加的便捷：
RGB转YUV
先说一下RGB转YUV的过程，先将RGB数据按照公式转换为YUV数据，然后将YUV数据按照RGBA进行排布，这一步的目的是为了后续数据读取，最后使用glReadPixels读取YUV数据。
而对于OpenGL ES来说，目前它输入只认RGBA、lumiance、luminace alpha这几个格式，输出大多数实现只认RGBA格式，因此输出的数据格式虽然是YUV格式，但是在存储时我们仍然要按照RGBA方式去访问texture数据。
以NV21的YUV数据为例，它的内存大小为width x height * 3 / 2。如果是RGBA的格式存储的话，占用的内存空间大小是width x height x 4（因为 RGBA 一共4个通道）。很显然它们的内存大小是对不上的， 那么该如何调整Opengl buffer的大小让RGBA的输出能对应上YUV的输出呢？我们可以设计输出的宽为width / 4，高为height * 3 / 2即可。
为什么是这样的呢？虽然我们的目的是将RGB转换成YUV，但是我们的输入和输出时读取的类型GLenum是依然是RGBA，也就是说：width x height x 4 = (width / 4) x (height * 3 / 2) * 4
而YUV数据在内存中的分布以下这样子的：
width / 4
|--------------|
| |
| | h
| Y |
|--------------|
| U | V |
| | | h / 2
|--------------|那么上面的排序如果进行了归一化之后呢，就变成了下面这样子了：
(0,0) width / 4 (1,0)
|--------------|
| |
| | h
| Y |
|--------------| (1,2/3)
| U | V |
| | | h / 2
|--------------|
(0,1) (1,1)从上面的排布可以看出看出，在纹理坐标y < (2/3)时，需要完成一次对整个纹理的采样，用于生成Y数据，当纹理坐标 y > (2/3)时，同样需要再进行一次对整个纹理的采样，用于生成UV的数据。同时还需要将我们的视窗设置为glViewport(0, 0, width / 4, height * 1.5);
由于视口宽度设置为原来的 1/4 ，可以简单的认为相对于原来的图像每隔4个像素做一次采样，由于我们生成Y数据是要对每一个像素都进行采样，所以还需要进行3次偏移采样。
同理，生成对于UV数据也需要进行3次额外的偏移采样。
在着色器中offset变量需要设置为一个归一化之后的值：1.0/width, 按照原理图，在纹理坐标 y < (2/3) 范围，一次采样（加三次偏移采样）4 个 RGBA 像素（R,G,B,A）生成 1 个（Y0,Y1,Y2,Y3），整个范围采样结束时填充好 width*height 大小的缓冲区；当纹理坐标 y > (2/3) 范围，一次采样（加三次偏移采样）4 个 RGBA 像素（R,G,B,A）生成 1 个（V0,U0,V0,U1），又因为 UV 缓冲区的高度为 height/2 ，VU plane 在垂直方向的采样是隔行进行，整个范围采样结束时填充好 width*height/2 大小的缓冲区。
主要代码
RGBtoYUVOpengl.cpp
#include "../utils/Log.h"
#include "RGBtoYUVOpengl.h"
// 顶点着色器
static const char *ver = "#version 300 esn"
"in vec4 aPosition;n"
"in vec2 aTexCoord;n"
"out vec2 v_texCoord;n"
"void main() {n"
" v_texCoord = aTexCoord;n"
" gl_Position = aPosition;n"
"}";
// 片元着色器
static const char *fragment = "#version 300 esn"
"precision mediump float;n"
"in vec2 v_texCoord;n"
"layout(location = 0) out vec4 outColor;n"
"uniform sampler2D s_TextureMap;n"
"uniform float u_Offset;n"
"const vec3 COEF_Y = vec3(0.299, 0.587, 0.114);n"
"const vec3 COEF_U = vec3(-0.147, -0.289, 0.436);n"
"const vec3 COEF_V = vec3(0.615, -0.515, -0.100);n"
"const float UV_DIVIDE_LINE = 2.0 / 3.0;n"
"void main(){n"
" vec2 texelOffset = vec2(u_Offset, 0.0);n"
" if (v_texCoord. y <= UV_DIVIDE_LINE) {n"
" vec2 texCoord = vec2(v_texCoord. x, v_texCoord. y * 3.0 / 2.0);n"
" vec4 color0 = texture(s_TextureMap, texCoord);n"
" vec4 color1 = texture(s_TextureMap, texCoord + texelOffset);n"
" vec4 color2 = texture(s_TextureMap, texCoord + texelOffset * 2.0);n"
" vec4 color3 = texture(s_TextureMap, texCoord + texelOffset * 3.0);n"
" float y0 = dot(color0. rgb, COEF_Y);n"
" float y1 = dot(color1. rgb, COEF_Y);n"
" float y2 = dot(color2. rgb, COEF_Y);n"
" float y3 = dot(color3. rgb, COEF_Y);n"
" outColor = vec4(y0, y1, y2, y3);n"
" } else {n"
" vec2 texCoord = vec2(v_texCoord.x, (v_texCoord.y - UV_DIVIDE_LINE) * 3.0);n"
" vec4 color0 = texture(s_TextureMap, texCoord);n"
" vec4 color1 = texture(s_TextureMap, texCoord + texelOffset);n"
" vec4 color2 = texture(s_TextureMap, texCoord + texelOffset * 2.0);n"
" vec4 color3 = texture(s_TextureMap, texCoord + texelOffset * 3.0);n"
" float v0 = dot(color0. rgb, COEF_V) + 0.5;n"
" float u0 = dot(color1. rgb, COEF_U) + 0.5;n"
" float v1 = dot(color2. rgb, COEF_V) + 0.5;n"
" float u1 = dot(color3. rgb, COEF_U) + 0.5;n"
" outColor = vec4(v0, u0, v1, u1);n"
" }n"
"}";
// 使用绘制两个三角形组成一个矩形的形式(三角形带)
// 第一第二第三个点组成一个三角形，第二第三第四个点组成一个三角形
const static GLfloat VERTICES[] = {
1.0f,-1.0f, // 右下
1.0f,1.0f, // 右上
-1.0f,-1.0f, // 左下
-1.0f,1.0f // 左上
};
// FBO贴图纹理坐标（参考手机屏幕坐标系统，原点在左下角）
// 注意坐标不要错乱
const static GLfloat TEXTURE_COORD[] = {
1.0f,0.0f, // 右下
1.0f,1.0f, // 右上
0.0f,0.0f, // 左下
0.0f,1.0f // 左上
};
RGBtoYUVOpengl::RGBtoYUVOpengl() {
initGlProgram(ver,fragment);
positionHandle = glGetAttribLocation(program,"aPosition");
textureHandle = glGetAttribLocation(program,"aTexCoord");
textureSampler = glGetUniformLocation(program,"s_TextureMap");
u_Offset = glGetUniformLocation(program,"u_Offset");
LOGD("program:%d",program);
LOGD("positionHandle:%d",positionHandle);
LOGD("textureHandle:%d",textureHandle);
LOGD("textureSample:%d",textureSampler);
LOGD("u_Offset:%d",u_Offset);
}
RGBtoYUVOpengl::~RGBtoYUVOpengl() noexcept {
}
void RGBtoYUVOpengl::fboPrepare() {
glGenTextures(1, &fboTextureId);
// 绑定纹理
glBindTexture(GL_TEXTURE_2D, fboTextureId);
// 为当前绑定的纹理对象设置环绕、过滤方式
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glBindTexture(GL_TEXTURE_2D, GL_NONE);
glGenFramebuffers(1,&fboId);
glBindFramebuffer(GL_FRAMEBUFFER,fboId);
// 绑定纹理
glBindTexture(GL_TEXTURE_2D,fboTextureId);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, fboTextureId, 0);
// 这个纹理是多大的？
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageWidth / 4, imageHeight * 1.5, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
// 检查FBO状态
if (glCheckFramebufferStatus(GL_FRAMEBUFFER)!= GL_FRAMEBUFFER_COMPLETE) {
LOGE("FBOSample::CreateFrameBufferObj glCheckFramebufferStatus status != GL_FRAMEBUFFER_COMPLETE");
}
// 解绑
glBindTexture(GL_TEXTURE_2D, GL_NONE);
glBindFramebuffer(GL_FRAMEBUFFER, GL_NONE);
}
// 渲染逻辑
void RGBtoYUVOpengl::onDraw() {
// 绘制到FBO上去
// 绑定fbo
glBindFramebuffer(GL_FRAMEBUFFER, fboId);
glPixelStorei(GL_UNPACK_ALIGNMENT,1);
// 设置视口大小
glViewport(0, 0,imageWidth / 4, imageHeight * 1.5);
glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(program);
// 激活纹理
glActiveTexture(GL_TEXTURE2);
glUniform1i(textureSampler, 2);
// 绑定纹理
glBindTexture(GL_TEXTURE_2D, textureId);
// 设置偏移
float texelOffset = (float) (1.f / (float) imageWidth);
glUniform1f(u_Offset,texelOffset);
/**
* size 几个数字表示一个点，显示是两个数字表示一个点
* normalized 是否需要归一化，不用，这里已经归一化了
* stride 步长，连续顶点之间的间隔，如果顶点直接是连续的，也可填0
*/
// 启用顶点数据
glEnableVertexAttribArray(positionHandle);
glVertexAttribPointer(positionHandle,2,GL_FLOAT,GL_FALSE,0,VERTICES);
// 纹理坐标
glEnableVertexAttribArray(textureHandle);
glVertexAttribPointer(textureHandle,2,GL_FLOAT,GL_FALSE,0,TEXTURE_COORD);
// 4个顶点绘制两个三角形组成矩形
glDrawArrays(GL_TRIANGLE_STRIP,0,4);
glUseProgram(0);
// 禁用顶点
glDisableVertexAttribArray(positionHandle);
if(nullptr != eglHelper){
eglHelper->swapBuffers();
}
glBindTexture(GL_TEXTURE_2D, 0);
// 解绑fbo
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
// 设置RGB图像数据
void RGBtoYUVOpengl::setPixel(void *data, int width, int height, int length) {
LOGD("texture setPixel");
imageWidth = width;
imageHeight = height;
// 准备fbo
fboPrepare();
glGenTextures(1, &textureId);
// 激活纹理，注意以下这个两句是搭配的，glActiveTexture激活的是那个纹理，就设置的sampler2D是那个
// 默认是0，如果不是0的话，需要在onDraw的时候重新激活一下？
// glActiveTexture(GL_TEXTURE0);
// glUniform1i(textureSampler, 0);
// 例如，一样的
glActiveTexture(GL_TEXTURE2);
glUniform1i(textureSampler, 2);
// 绑定纹理
glBindTexture(GL_TEXTURE_2D, textureId);
// 为当前绑定的纹理对象设置环绕、过滤方式
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
// 生成mip贴图
glGenerateMipmap(GL_TEXTURE_2D);
// 解绑定
glBindTexture(GL_TEXTURE_2D, 0);
}
// 读取渲染后的YUV数据
void RGBtoYUVOpengl::readYUV(uint8_t **data, int *width, int *height) {
// 从fbo中读取
// 绑定fbo
*width = imageWidth;
*height = imageHeight;
glBindFramebuffer(GL_FRAMEBUFFER, fboId);
glBindTexture(GL_TEXTURE_2D, fboTextureId);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D, fboTextureId, 0);
*data = new uint8_t[imageWidth * imageHeight * 3 / 2];
glReadPixels(0, 0, imageWidth / 4, imageHeight * 1.5, GL_RGBA, GL_UNSIGNED_BYTE, *data);
glBindTexture(GL_TEXTURE_2D, 0);
// 解绑fbo
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
下面是Activity的主要代码逻辑：
public class RGBToYUVActivity extends AppCompatActivity {
protected MyGLSurfaceView myGLSurfaceView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rgb_to_yuv);
myGLSurfaceView = findViewById(R.id.my_gl_surface_view);
myGLSurfaceView.setOpenGlListener(new MyGLSurfaceView.OnOpenGlListener() {
@Override
public BaseOpengl onOpenglCreate() {
return new RGBtoYUVOpengl();
}
@Override
public Bitmap requestBitmap() {
BitmapFactory.Options options = new BitmapFactory.Options();
options.inScaled = false;
return BitmapFactory.decodeResource(getResources(),R.mipmap.ic_smile,options);
}
@Override
public void readPixelResult(byte[] bytes) {
if (null != bytes) {
}
}
// 也就是RGBtoYUVOpengl::readYUV读取到结果数据回调
@Override
public void readYUVResult(byte[] bytes) {
if (null != bytes) {
String fileName = System.currentTimeMillis() + ".yuv";
File fileParent = getFilesDir();
if (!fileParent.exists()) {
fileParent.mkdirs();
}
FileOutputStream fos = null;
try {
File file = new File(fileParent, fileName);
fos = new FileOutputStream(file);
fos.write(bytes,0,bytes.length);
fos.flush();
fos.close();
Toast.makeText(RGBToYUVActivity.this, "YUV图片保存成功" + file.getAbsolutePath(), Toast.LENGTH_LONG).show();
} catch (Exception e) {
Log.v("fly_learn_opengl", "图片保存异常：" + e.getMessage());
Toast.makeText(RGBToYUVActivity.this, "YUV图片保存失败", Toast.LENGTH_LONG).show();
}
}
}
});
Button button = findViewById(R.id.bt_rgb_to_yuv);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
myGLSurfaceView.readYuvData();
}
});
ImageView iv_rgb = findViewById(R.id.iv_rgb);
iv_rgb.setImageResource(R.mipmap.ic_smile);
}
}以下是自定义SurfaceView的代码：
public class MyGLSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
private final static int MSG_CREATE_GL = 101;
private final static int MSG_CHANGE_GL = 102;
private final static int MSG_DRAW_GL = 103;
private final static int MSG_DESTROY_GL = 104;
private final static int MSG_READ_PIXEL_GL = 105;
private final static int MSG_UPDATE_BITMAP_GL = 106;
private final static int MSG_UPDATE_YUV_GL = 107;
private final static int MSG_READ_YUV_GL = 108;
public BaseOpengl baseOpengl;
private OnOpenGlListener onOpenGlListener;
private HandlerThread handlerThread;
private Handler renderHandler;
public int surfaceWidth;
public int surfaceHeight;
public MyGLSurfaceView(Context context) {
this(context,null);
}
public MyGLSurfaceView(Context context, AttributeSet attrs) {
super(context, attrs);
getHolder().addCallback(this);
handlerThread = new HandlerThread("RenderHandlerThread");
handlerThread.start();
renderHandler = new Handler(handlerThread.getLooper()){
@Override
public void handleMessage(@NonNull Message msg) {
switch (msg.what){
case MSG_CREATE_GL:
baseOpengl = onOpenGlListener.onOpenglCreate();
Surface surface = (Surface) msg.obj;
if(null != baseOpengl){
baseOpengl.surfaceCreated(surface);
Bitmap bitmap = onOpenGlListener.requestBitmap();
if(null != bitmap){
baseOpengl.setBitmap(bitmap);
}
}
break;
case MSG_CHANGE_GL:
if(null != baseOpengl){
Size size = (Size) msg.obj;
baseOpengl.surfaceChanged(size.getWidth(),size.getHeight());
}
break;
case MSG_DRAW_GL:
if(null != baseOpengl){
baseOpengl.onGlDraw();
}
break;
case MSG_READ_PIXEL_GL:
if(null != baseOpengl){
byte[] bytes = baseOpengl.readPixel();
if(null != bytes && null != onOpenGlListener){
onOpenGlListener.readPixelResult(bytes);
}
}
break;
case MSG_READ_YUV_GL:
if(null != baseOpengl){
byte[] bytes = baseOpengl.readYUVResult();
if(null != bytes && null != onOpenGlListener){
onOpenGlListener.readYUVResult(bytes);
}
}
break;
case MSG_UPDATE_BITMAP_GL:
if(null != baseOpengl){
Bitmap bitmap = onOpenGlListener.requestBitmap();
if(null != bitmap){
baseOpengl.setBitmap(bitmap);
baseOpengl.onGlDraw();
}
}
break;
case MSG_UPDATE_YUV_GL:
if(null != baseOpengl){
YUVBean yuvBean = (YUVBean) msg.obj;
if(null != yuvBean){
baseOpengl.setYuvData(yuvBean.getyData(),yuvBean.getUvData(),yuvBean.getWidth(),yuvBean.getHeight());
baseOpengl.onGlDraw();
}
}
break;
case MSG_DESTROY_GL:
if(null != baseOpengl){
baseOpengl.surfaceDestroyed();
}
break;
}
}
};
}
public void setOpenGlListener(OnOpenGlListener listener) {
this.onOpenGlListener = listener;
}
@Override
public void surfaceCreated(@NonNull SurfaceHolder surfaceHolder) {
Message message = Message.obtain();
message.what = MSG_CREATE_GL;
message.obj = surfaceHolder.getSurface();
renderHandler.sendMessage(message);
}
@Override
public void surfaceChanged(@NonNull SurfaceHolder surfaceHolder, int i, int w, int h) {
Message message = Message.obtain();
message.what = MSG_CHANGE_GL;
message.obj = new Size(w,h);
renderHandler.sendMessage(message);
Message message1 = Message.obtain();
message1.what = MSG_DRAW_GL;
renderHandler.sendMessage(message1);
surfaceWidth = w;
surfaceHeight = h;
}
@Override
public void surfaceDestroyed(@NonNull SurfaceHolder surfaceHolder) {
Message message = Message.obtain();
message.what = MSG_DESTROY_GL;
renderHandler.sendMessage(message);
}
public void readGlPixel(){
Message message = Message.obtain();
message.what = MSG_READ_PIXEL_GL;
renderHandler.sendMessage(message);
}
public void readYuvData(){
Message message = Message.obtain();
message.what = MSG_READ_YUV_GL;
renderHandler.sendMessage(message);
}
public void updateBitmap(){
Message message = Message.obtain();
message.what = MSG_UPDATE_BITMAP_GL;
renderHandler.sendMessage(message);
}
public void setYuvData(byte[] yData,byte[] uvData,int width,int height){
Message message = Message.obtain();
message.what = MSG_UPDATE_YUV_GL;
message.obj = new YUVBean(yData,uvData,width,height);
renderHandler.sendMessage(message);
}
public void release(){
// todo 主要线程同步问题，当心surfaceDestroyed还没有执行到，但是就被release了，那就内存泄漏了
if(null != baseOpengl){
baseOpengl.release();
}
}
public void requestRender(){
Message message = Message.obtain();
message.what = MSG_DRAW_GL;
renderHandler.sendMessage(message);
}
public interface OnOpenGlListener{
BaseOpengl onOpenglCreate();
Bitmap requestBitmap();
void readPixelResult(byte[] bytes);
void readYUVResult(byte[] bytes);
}
}BaseOpengl的java代码：
public class BaseOpengl {
public static final int YUV_DATA_TYPE_NV12 = 0;
public static final int YUV_DATA_TYPE_NV21 = 1;
// 三角形
public static final int DRAW_TYPE_TRIANGLE = 0;
// 四边形
public static final int DRAW_TYPE_RECT = 1;
// 纹理贴图
public static final int DRAW_TYPE_TEXTURE_MAP = 2;
// 矩阵变换
public static final int DRAW_TYPE_MATRIX_TRANSFORM = 3;
// VBO/VAO
public static final int DRAW_TYPE_VBO_VAO = 4;
// EBO
public static final int DRAW_TYPE_EBO_IBO = 5;
// FBO
public static final int DRAW_TYPE_FBO = 6;
// PBO
public static final int DRAW_TYPE_PBO = 7;
// YUV nv12与nv21渲染
public static final int DRAW_YUV_RENDER = 8;
// 将rgb图像转换城nv21
public static final int DRAW_RGB_TO_YUV = 9;
public long glNativePtr;
protected EGLHelper eglHelper;
protected int drawType;
public BaseOpengl(int drawType) {
this.drawType = drawType;
this.eglHelper = new EGLHelper();
}
public void surfaceCreated(Surface surface) {
Log.v("fly_learn_opengl","------------surfaceCreated:" + surface);
eglHelper.surfaceCreated(surface);
}
public void surfaceChanged(int width, int height) {
Log.v("fly_learn_opengl","------------surfaceChanged:" + Thread.currentThread());
eglHelper.surfaceChanged(width,height);
}
public void surfaceDestroyed() {
Log.v("fly_learn_opengl","------------surfaceDestroyed:" + Thread.currentThread());
eglHelper.surfaceDestroyed();
}
public void release(){
if(glNativePtr != 0){
n_free(glNativePtr,drawType);
glNativePtr = 0;
}
}
public void onGlDraw(){
Log.v("fly_learn_opengl","------------onDraw:" + Thread.currentThread());
if(glNativePtr == 0){
glNativePtr = n_gl_nativeInit(eglHelper.nativePtr,drawType);
}
if(glNativePtr != 0){
n_onGlDraw(glNativePtr,drawType);
}
}
public void setBitmap(Bitmap bitmap){
if(glNativePtr == 0){
glNativePtr = n_gl_nativeInit(eglHelper.nativePtr,drawType);
}
if(glNativePtr != 0){
n_setBitmap(glNativePtr,bitmap);
}
}
public void setYuvData(byte[] yData,byte[] uvData,int width,int height){
if(glNativePtr != 0){
n_setYuvData(glNativePtr,yData,uvData,width,height,drawType);
}
}
public void setMvpMatrix(float[] mvp){
if(glNativePtr == 0){
glNativePtr = n_gl_nativeInit(eglHelper.nativePtr,drawType);
}
if(glNativePtr != 0){
n_setMvpMatrix(glNativePtr,mvp);
}
}
public byte[] readPixel(){
if(glNativePtr != 0){
return n_readPixel(glNativePtr,drawType);
}
return null;
}
public byte[] readYUVResult(){
if(glNativePtr != 0){
return n_readYUV(glNativePtr,drawType);
}
return null;
}
// 绘制
private native void n_onGlDraw(long ptr,int drawType);
private native void n_setMvpMatrix(long ptr,float[] mvp);
private native void n_setBitmap(long ptr,Bitmap bitmap);
protected native long n_gl_nativeInit(long eglPtr,int drawType);
private native void n_free(long ptr,int drawType);
private native byte[] n_readPixel(long ptr,int drawType);
private native byte[] n_readYUV(long ptr,int drawType);
private native void n_setYuvData(long ptr,byte[] yData,byte[] uvData,int width,int height,int drawType);
}将转换后的YUV数据读取保存好后，可以将数据拉取到电脑上使用YUVViewer这个软件查看是否真正转换成功。
参考
https://juejin.cn/post/7025223104569802789
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