作者:字节流动
来源:https://blog.csdn.net/Kennethdroid/article/details/103189489
penGL ES 相机预览
相机开发是 OpenGL ES 的重要应用,利用 OpenGL 可以很方便地实现相机美颜、滤镜、塑型以及一些动态特效,其性能显著优于对应功能的 CPU 实现。
相机的预览实现一般有 2 种方式,一种是基于 Android 原生 SurfaceTexture 的纯 GPU 实现方式,另一种是通过相机的预览回调接口获取帧的 YUV 数据,利用 CPU 算法处理完成之后,传入显存,再利用 GPU 实现 YUV 转 RGBA 进行渲染,即 CPU + GPU 的实现方式。
基于 Android 原生 SurfaceTexture 的纯 GPU 实现方式,相机可以使用 SurfaceTexture 作为预览载体,SurfaceTexture 可来自于 GLSurfaceView、TextureView 或 SurfaceView 这些独立拥有 Surface 的封装类,也可以自定义实现。
作为预览载体的 SurfaceTexture 绑定的纹理需要是 OES 纹理,即 GLES11Ext.GL_TEXTURE_EXTERNAL_OES
纹理,来自于 GLES 的扩展 #extension GL_OES_EGL_image_external
中,使用 OES 纹理后,我们不需要在片段着色器中自己做 YUV to RGBA 的转换,因为 OES 纹理可以直接接收 YUV 数据或者直接输出 YUV 数据。
类似于普通 2D 纹理的创建,OES 纹理创建的实现如下:
private int createOESTexture(){ int[] texture = new int[1]; GLES20.glGenTextures(1, texture, 0); GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture[0]); GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_LINEAR); GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE); GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE); return texture[0]; }
使用 OES 纹理需要修改片段着色器,在着色器脚本的头部增加扩展纹理的声明 #extension GL_OES_EGL_image_external : require
,并且纹理采样器不再使用 sample2D ,需要换成 samplerExternalOES 作为纹理采样器。
#version 300 es #extension GL_OES_EGL_image_external : require precision mediump float; in vec2 v_texCoord; uniform samplerExternalOES s_TexSampler; void main() { gl_FragColor = texture(s_TexSampler, v_texCoord); }
实际上当使用 TextureView 时,实际上也不需要自己去创建 OES 纹理,只需要绑定相机,配置好变换矩阵后即可实现相机预览。具体例子可直接参考Android 官方的 Samples https://github.com/android/camera-samples 。
相机预览基于 Android 原生 API 的纯 GPU 实现方式,操作简单,代码量很少,原生 API 已经做了很多封装,可以利用片段着色器轻易实现美颜滤镜等相机特效,缺点是扩展性差,例如要使用传统的 CPU 算法做一些滤镜或者美颜特效就很不方便,图像数据需要多次在内存与显存之间拷贝,会造成性能和功耗问题。
本文主要介绍将图像数据取出,传入 Native 层,然后对数据做一些处理(可选),最后再做渲染的方式,这种方式相对复杂一些。相机预览数据的常见格式是 YUV420P 或者 YUV420SP(NV21) ,需要将图像数据对应 YUV 3 个分量使用 3 个纹理传入显存,在片段着色器中将 YUV 数据转为 RGBA 。
相关原理可参考NDK OpenGL ES 3.0 开发(三):YUV 渲染 章节。
相机预览数据获取,以 Camera2 为例,主要是通过 ImageReader 实现,该类封装了 Surface :
private ImageReader.OnImageAvailableListener mOnPreviewImageAvailableListener = new ImageReader.OnImageAvailableListener() { @Override public void onImageAvailable(ImageReader reader) { Image image = reader.acquireLatestImage(); if (image != null) { if (mCamera2FrameCallback != null) { mCamera2FrameCallback.onPreviewFrame(CameraUtil.YUV_420_888_data(image), image.getWidth(), image.getHeight()); } image.close(); } } }; mPreviewImageReader = ImageReader.newInstance(mPreviewSize.getWidth(), mPreviewSize.getHeight(), ImageFormat.YUV_420_888, 2); mPreviewImageReader.setOnImageAvailableListener(mOnPreviewImageAvailableListener, mBackgroundHandler); CaptureRequest.Builder builder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); builder.addTarget(mPreviewImageReader.getSurface()); ession.setRepeatingRequest(mPreviewRequest, null, mBackgroundHandler); //在自定义接口中获取预览数据,通过 JNI 传入到 C++ 层 public void onPreviewFrame(byte[] data, int width, int height) { Log.d(TAG, "onPreviewFrame() called with: data = [" + data + "], width = [" + width + "], height = [" + height + "]"); mByteFlowRender.setRenderFrame(IMAGE_FORMAT_I420, data, width, height); //每次传入新数据,请求重新渲染 mByteFlowRender.requestRender(); }
主要的 JNI :
public abstract class ByteFlowRender { public static final int GL_RENDER_TYPE = 0; public static final int CL_RENDER_TYPE = 1; public static final int IMAGE_FORMAT_RGBA = 0x01; public static final int IMAGE_FORMAT_NV21 = 0x02; public static final int IMAGE_FORMAT_NV12 = 0x03; public static final int IMAGE_FORMAT_I420 = 0x04; public static final int PARAM_TYPE_SET_SHADER_INDEX = 201; static { System.loadLibrary("byteflow_render"); } private long mNativeContextHandle; protected native void native_CreateContext(int renderType); protected native void native_DestroyContext(); protected native int native_Init(int initType); protected native int native_UnInit(); protected native void native_UpdateFrame(int format, byte[] data, int width, int height); protected native void native_LoadFilterData(int index, int format, int width, int height, byte[] bytes); protected native void native_LoadShaderScript(int shaderIndex, String scriptStr); protected native void native_SetTransformMatrix(float translateX, float translateY, float scaleX, float scaleY, int degree, int mirror); protected native void native_SetParamsInt(int paramType, int value); protected native int native_GetParamsInt(int paramType); protected native void native_OnSurfaceCreated(); protected native void native_OnSurfaceChanged(int width, int height); protected native void native_OnDrawFrame(); }
渲染 YUV 数据用到的着色器脚本,主要是将 3 个纹理对应的 YUV 分量,分别采样后转成 RGBA :
//顶点着色器 #version 100 varying vec2 v_texcoord; attribute vec4 position; attribute vec2 texcoord; uniform mat4 MVP; void main() { v_texcoord = texcoord; gl_Position = MVP*position; } //片段着色器 #version 100 precision highp float; varying vec2 v_texcoord; uniform lowp sampler2D s_textureY; uniform lowp sampler2D s_textureU; uniform lowp sampler2D s_textureV; void main() { float y, u, v, r, g, b; y = texture2D(s_textureY, v_texcoord).r; u = texture2D(s_textureU, v_texcoord).r; v = texture2D(s_textureV, v_texcoord).r; u = u - 0.5; v = v - 0.5; r = y + 1.403 * v; g = y - 0.344 * u - 0.714 * v; b = y + 1.770 * u; gl_FragColor = vec4(r, g, b, 1.0); }
C++ 层的主要实现:
//编译链接着色器 int GLByteFlowRender::CreateProgram(const char *pVertexShaderSource, const char *pFragShaderSource) { m_Program = GLUtils::CreateProgram(pVertexShaderSource, pFragShaderSource, m_VertexShader, m_FragShader); if (!m_Program) { GLUtils::CheckGLError("Create Program"); LOGCATE("GLByteFlowRender::CreateProgram Could not create program."); return 0; } m_YTextureHandle = glGetUniformLocation(m_Program, "s_textureY"); m_UTextureHandle = glGetUniformLocation(m_Program, "s_textureU"); m_VTextureHandle = glGetUniformLocation(m_Program, "s_textureV"); m_VertexCoorHandle = (GLuint) glGetAttribLocation(m_Program, "position"); m_TextureCoorHandle = (GLuint) glGetAttribLocation(m_Program, "texcoord"); m_MVPHandle = glGetUniformLocation(m_Program, "MVP"); return m_Program; } //创建 YUV 分量对应的 3 个纹理 bool GLByteFlowRender::CreateTextures() { LOGCATE("GLByteFlowRender::CreateTextures"); GLsizei yWidth = static_cast<GLsizei>(m_RenderFrame.width); GLsizei yHeight = static_cast<GLsizei>(m_RenderFrame.height); glActiveTexture(GL_TEXTURE0); glGenTextures(1, &m_YTextureId); glBindTexture(GL_TEXTURE_2D, m_YTextureId); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(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); glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, yWidth, yHeight, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL); if (!m_YTextureId) { GLUtils::CheckGLError("Create Y texture"); return false; } GLsizei uWidth = static_cast<GLsizei>(m_RenderFrame.width / 2); GLsizei uHeight = yHeight / 2; glActiveTexture(GL_TEXTURE1); glGenTextures(1, &m_UTextureId); glBindTexture(GL_TEXTURE_2D, m_UTextureId); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(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); glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, uWidth, uHeight, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL); if (!m_UTextureId) { GLUtils::CheckGLError("Create U texture"); return false; } GLsizei vWidth = static_cast<GLsizei>(m_RenderFrame.width / 2); GLsizei vHeight = (GLsizei) yHeight / 2; glActiveTexture(GL_TEXTURE2); glGenTextures(1, &m_VTextureId); glBindTexture(GL_TEXTURE_2D, m_VTextureId); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(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); glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, vWidth, vHeight, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, NULL); if (!m_VTextureId) { GLUtils::CheckGLError("Create V texture"); return false; } return true; } //每传入一帧新数据后,更新纹理 bool GLByteFlowRender::UpdateTextures() { LOGCATE("GLByteFlowRender::UpdateTextures"); if (m_RenderFrame.ppPlane[0] == NULL) { return false; } if (!m_YTextureId && !m_UTextureId && !m_VTextureId && !CreateTextures()) { return false; } glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, m_YTextureId); glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, (GLsizei) m_RenderFrame.width, (GLsizei) m_RenderFrame.height, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, m_RenderFrame.ppPlane[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, m_UTextureId); glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, (GLsizei) m_RenderFrame.width >> 1, (GLsizei) m_RenderFrame.height >> 1, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, m_RenderFrame.ppPlane[1]); glActiveTexture(GL_TEXTURE2); glBindTexture(GL_TEXTURE_2D, m_VTextureId); glTexImage2D(GL_TEXTURE_2D, 0, GL_LUMINANCE, (GLsizei) m_RenderFrame.width >> 1, (GLsizei) m_RenderFrame.height >> 1, 0, GL_LUMINANCE, GL_UNSIGNED_BYTE, m_RenderFrame.ppPlane[2]); return true; } //绑定纹理到着色器,传入顶点和纹理坐标数据 GLuint GLByteFlowRender::UseProgram() { LOGCATE("GLByteFlowRender::UseProgram"); ByteFlowLock lock(&m_ShaderBufLock); if (m_IsShaderChanged) { GLUtils::DeleteProgram(m_Program); CreateProgram(kVertexShader, m_pFragShaderBuf); m_IsShaderChanged = false; m_IsProgramChanged = true; } if (!m_Program) { LOGCATE("GLByteFlowRender::UseProgram Could not use program."); return 0; } if (m_IsProgramChanged) { glUseProgram(m_Program); GLUtils::CheckGLError("GLByteFlowRender::UseProgram"); glVertexAttribPointer(m_VertexCoorHandle, 2, GL_FLOAT, GL_FALSE, 2 * 4, VERTICES_COORS); glEnableVertexAttribArray(m_VertexCoorHandle); glUniform1i(m_YTextureHandle, 0); glUniform1i(m_UTextureHandle, 1); glUniform1i(m_VTextureHandle, 2); glVertexAttribPointer(m_TextureCoorHandle, 2, GL_FLOAT, GL_FALSE, 2 * 4, TEXTURE_COORS); glEnableVertexAttribArray(m_TextureCoorHandle); m_IsProgramChanged = false; } return m_Program; } //渲染预览图像 void GLByteFlowRender::OnDrawFrame() { LOGCATE("GLByteFlowRender::OnDrawFrame"); glViewport(0, 0, m_ViewportWidth, m_ViewportHeight); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glClearColor(0.0f, 0.0f, 0.0f, 1.0f); glDisable(GL_CULL_FACE); if (!UpdateTextures() || !UseProgram()) { LOGCATE("GLByteFlowRender::OnDrawFrame skip frame"); return; } glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); }
后面文章会基于该预览实现添加一些滤镜效果。
联系与交流
技术交流/获取源码可以添加我的微信:Byte-Flow
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