我正在尝试使用 NDK、JNI 在 Android Studio 上制作一个简单的应用程序来调用加载和显示图像的 C++ 代码。我已经成功创建了曲面并绘制了一个简单的三角形。
现在，我正在寻找一种使用 C++ 在 OpenGL ES 3.0 中加载和显示图像的方法。我已经进行了搜索，但所有这些对我来说要么太复杂，要么过时或用 Java 编写。如果有人可以用一个简单的例子来指导我，那就太好了。
经过一番努力，终于成功了。下面是我的 C++ 源代码。我使用 stb_image 库来加载图像。
/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// OpenGL ES 3.0 code
#include <jni.h>
#include <android/log.h>
#include <GLES3/gl3.h>
#include <GLES3/gl3ext.h>
#include <GLES3/gl3ext.h>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "stb_image.h"
#define LOG_TAG "libgl2jni"
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
GLuint mTexture, VAO;// Create reference Id for the texture
GLuint gProgram;
GLuint gvPositionHandle;
static void printGLString(const char *name, GLenum s) {
const char *v = (const char *) glGetString(s);
LOGI("GL %s = %s\n", name, v);
}
static void checkGlError(const char* op) {
for (GLint error = glGetError(); error; error
= glGetError()) {
LOGI("after %s() glError (0x%x)\n", op, error);
}
}
auto gVertexShader =
"#version 300 es\n"
"layout (location=0) in vec3 position;\n"
"layout (location=1) in vec3 color;\n"
"layout (location=2) in vec2 texCoord;\n"
"out vec3 ourColor;\n"
"out vec2 TexCoord;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(position,1.0f); // Add the xOffset to the x position of the vertex position\n"
"ourColor = color;\n"
"TexCoord= vec2(texCoord.x,1.0f-texCoord.y);\n"
"}";
auto gFragmentShader =
"#version 300 es\n"
"in vec3 ourColor;\n"
"in vec2 TexCoord;\n"
"out vec4 color;\n"
"uniform sampler2D ourTexture;\n"
"void main()\n"
"{\n"
"color = texture(ourTexture , TexCoord);\n"
"}\n";
GLuint loadShader(GLenum shaderType, const char* pSource) {
GLuint shader = glCreateShader(shaderType);
if (shader) {
glShaderSource(shader, 1, &pSource, NULL);
glCompileShader(shader);
GLint compiled = 0;
glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
if (!compiled) {
GLint infoLen = 0;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
if (infoLen) {
char* buf = (char*) malloc(infoLen);
if (buf) {
glGetShaderInfoLog(shader, infoLen, NULL, buf);
LOGE("Could not compile shader %d:\n%s\n",
shaderType, buf);
free(buf);
}
glDeleteShader(shader);
shader = 0;
}
}
}
return shader;
}
GLuint createProgram(const char* pVertexSource, const char* pFragmentSource) { // Load and Bind Fragments to Progam and link program then return result
GLuint vertexShader = loadShader(GL_VERTEX_SHADER, pVertexSource);
if (!vertexShader) {
return 0;
}
GLuint pixelShader = loadShader(GL_FRAGMENT_SHADER, pFragmentSource);
if (!pixelShader) {
return 0;
}
GLuint program = glCreateProgram();
if (program) {
glAttachShader(program, vertexShader);
checkGlError("glAttachShader");
glAttachShader(program, pixelShader);
checkGlError("glAttachShader");
glLinkProgram(program);
GLint linkStatus = GL_FALSE;
glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
if (linkStatus != GL_TRUE) {
GLint bufLength = 0;
glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
if (bufLength) {
char* buf = (char*) malloc(bufLength);
if (buf) {
glGetProgramInfoLog(program, bufLength, NULL, buf);
LOGE("Could not link program:\n%s\n", buf);
free(buf);
}
}
glDeleteProgram(program);
program = 0;
}
}
return program;
}
bool setupGraphics(int w, int h) {
printGLString("Version", GL_VERSION);
printGLString("Vendor", GL_VENDOR);
printGLString("Renderer", GL_RENDERER);
printGLString("Extensions", GL_EXTENSIONS);
LOGI("setupGraphics(%d, %d)", w, h);
gProgram = createProgram(gVertexShader, gFragmentShader);
if (!gProgram) {
LOGE("Could not create program.");
return false;
}
gvPositionHandle = glGetAttribLocation(gProgram, "position");
checkGlError("glGetAttribLocation");
LOGI("glGetAttribLocation(\"position\") = %d\n",
gvPositionHandle);
glViewport(0, 0, w, h);
checkGlError("glViewport");
return true;
}
GLfloat recVertices[] = {
// Positions // Colors // Texture Coords
0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // Top Right
0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // Bottom Right
-0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // Bottom Left
-0.5f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f // Top Left
};
GLuint indices[] = { // Note that we start from 0!
0, 1, 3, // First Triangle
1, 2, 3 // Second Triangle
};
void initBuffers()
{
GLuint VBOs[2], EBO; // Initialize an buffer to store all the verticles and transfer them to the GPU
glGenVertexArrays (1,&VAO); // Generate VAO
glGenBuffers(1, VBOs); // Generate VBO
glGenBuffers(1, &EBO); // Generate EBO
glBindVertexArray (VAO);// Bind the Vertex Array
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);//Bind verticles array for OpenGL to use
glBufferData(GL_ARRAY_BUFFER, sizeof(recVertices), recVertices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);//Bind the indices for information about drawing sequence
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
// 1. set the vertex attributes pointers
// Position Attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(0);
// Color Attribute
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glEnableVertexAttribArray(1);
//Texture Coordinate Attribute
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(GLfloat), (GLvoid*)(6 * sizeof(GLfloat)));
glEnableVertexAttribArray(2);
glBindVertexArray(0);//3. Unbind VAO
}
void generateTexture()
{
glGenTextures(1 , &mTexture);
glBindTexture(GL_TEXTURE_2D, mTexture);// Bind our 2D texture so that following set up will be applied
//Set texture wrapping parameter
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_MIRRORED_REPEAT);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_MIRRORED_REPEAT);
//Set texture Filtering parameter
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
//Load the image
int picWidth,picHeight,n;
unsigned char* image = stbi_load("/storage/emulated/sdcard/Lighthouse.jpg", &picWidth, &picHeight, &n,0);
if (image == NULL ) {
LOGI("Failed to load image: %s", stbi_failure_reason());
}
//Generate the image
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB , picWidth , picHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
glGenerateMipmap(GL_TEXTURE_2D);
stbi_image_free(image);// Free the reference to the image
glBindTexture(GL_TEXTURE_2D,0); //Unbind 2D textures
}
void renderFrame() {
static float grey;
grey += 0.01f;
if (grey > 1.0f) {
grey = 0.0f;
}
generateTexture();
glClearColor(grey+0.05f, grey-0.03f, grey+0.02f, grey-0.04f);
checkGlError("glClearColor");
glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
checkGlError("glClear");
glUseProgram(gProgram);
checkGlError("glUseProgram");
/*glVertexAttribPointer(gvPositionHandle, 2, GL_FLOAT, GL_FALSE, 0, recVertices);
checkGlError("glVertexAttribPointer");
glEnableVertexAttribArray(gvPositionHandle);
checkGlError("glEnableVertexAttribArray");
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
checkGlError("glDrawArrays");*/
glActiveTexture(GL_TEXTURE0);
checkGlError("glActiveTexture");
glBindTexture(GL_TEXTURE_2D,mTexture);
checkGlError("glBindTexture");
GLint mlocation = glGetUniformLocation(gProgram,"ourTexture");
checkGlError("glGetUniformLocation");
glUniform1i(mlocation,0);
checkGlError("glUniform1i");
initBuffers();
glBindVertexArray(VAO);
checkGlError("glBindVertexArray");
glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0);
}
extern "C" {
JNIEXPORT void JNICALL Java_com_android_gles3jni_GLES3JNILib_init(JNIEnv * env, jobject obj, jint width, jint height);
JNIEXPORT void JNICALL Java_com_android_gles3jni_GLES3JNILib_step(JNIEnv * env, jobject obj);
};
JNIEXPORT void JNICALL Java_com_android_gles3jni_GLES3JNILib_init(JNIEnv * env, jobject obj, jint width, jint height)
{
setupGraphics(width, height);
}
JNIEXPORT void JNICALL Java_com_android_gles3jni_GLES3JNILib_step(JNIEnv * env, jobject obj)
{
renderFrame();
}
我无法构建您在 ans 中给出的代码，我正在使用 hello-gl2 ndk 示例应用程序。