[英]Display a pgm image using openGl
So i am writing a program using openGl on C++.I want to load an image and then display it in a NxN grid form. 所以我正在C ++上使用openGl编写程序。我想加载图像,然后以NxN网格形式显示它。 I loaded the image and stored its data in an array and then proceeded to use the following method to achieve my goal:
我加载了图像并将其数据存储在数组中,然后继续使用以下方法来实现我的目标:
void fillGrid(){
ifstream myfile("paper.pgm");
ofstream otherfile;
otherfile.open("test.txt");
string line;
string buffer;
fstream afile;
if (myfile.is_open())
{
int counter=0;
while (getline(myfile, line))
{
if(counter>2){
buffer=buffer+line;
}
counter++;
}
pixels=new float[1600];
int i=0;
string delimiters = " ,";
size_t current;
size_t next = -1;
do
{
current = next + 1;
next = buffer.find_first_of( delimiters, current );
if(i<=1600){
pixels[i]=myAtof (buffer.substr(current));
paper[i]=pixels[i];
}
i++;
}
while (next != string::npos);
for(int j=0;j<=1600;j++){
otherfile<<paper[j]<<" "<< j<<endl;
}
glEnable(GL_TEXTURE_2D);
glEnable(GL_DEPTH_TEST);
glBindTexture(GL_TEXTURE_2D, 1);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 140, 140, 0, GL_RGB, GL_FLOAT, paper);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_REPEAT);
}
}
This function opens the file containing the image data, loads the image in the pixels array at first and then at the paper array that i use in glTexImage2D. 此函数将打开包含图像数据的文件,首先将图像加载到pixel数组中,然后再加载到我在glTexImage2D中使用的纸张数组中。 MyAtof() is a function i built to convert a string into a float.
MyAtof()是我构建的用于将字符串转换为浮点型的函数。 The data is properly passed from the file to the array, i've tested it.
数据已正确地从文件传递到数组,我已经对其进行了测试。 After ther fillGrid function the following function is called t do the repaint:
在fillGrid函数之后,以下函数被称为t重新绘制:
void drawGrid2(void)
{
for(int i=-240;i<240;i+=40){
for(int j=-300;j<=300;j+=40){
drawSquare2(i,j);
}
}
}
And also: 并且:
void drawSquare2(int x,int y)
{
glBindTexture(GL_TEXTURE_2D, 1);
glBegin(GL_QUADS); //Start drawing quad
glVertex2f(x,y); //first coordinate x y
glVertex2f(x+40,y); //second coordinate
glVertex2f(x+40,y+40); //third coordinate
glVertex2f(x,y+40); //last coordinate
glEnd(); //Stop drawing quads
glFlush ();
}
Main: 主要:
int main (int argc, char** argv)
{
glutInit (&argc, argv); // Initialize GLUT.
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); // Set display mode.
glutInitWindowPosition (0, 0); // Set top-left display-window position.
glutInitWindowSize (600, 500); // Set display-window width and height.
glutCreateWindow ("Main"); // Create display window.
init (); // Execute initialization procedure.
glutDisplayFunc (display); // Send graphics to display window.
glutKeyboardFunc(processEscKey);
glutMainLoop (); // Display everything and wait.
return 0;
}
Other functions: 其他功能:
void init (void)
{
// glClearColor (1.0, 1.0, 1.0, 0.0); // Set display-window color to white.
glClearColor (0.0, 0.0, 0.0, 1.0);//black
glClear (GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glMatrixMode (GL_PROJECTION); // Set projection parameters.
gluOrtho2D(-300,300,-300,300);//0,width,0,height
}
void processEscKey(unsigned char key, int x, int y)
{
if(key==27){
exit(0);
}
else if(key==98){
fillGrid();
drawGrid2();
}
}
Is this the correct way to create a texture and display an image with openGl? 这是使用openGl创建纹理并显示图像的正确方法吗?
The file compiles but the result isn't what i want. 该文件编译,但结果不是我想要的。 I wanted an 15x15 grid of squares, with each square containing the image.
我想要一个15x15的正方形网格,每个正方形都包含图像。 Before the repaint the result was this .
在重新粉刷之前,结果是this 。
After the repaint the result is this . 重新粉刷后的结果是this 。
I used different functions for the first repaint and the the second one. 我为第一次重涂和第二次重涂使用了不同的功能。 Since the first one is working i didnt post it.
由于第一个工作,所以我没有发布它。
OpenGL's default texture minification filter is GL_NEAREST_MIPMAP_LINEAR
. OpenGL的默认纹理缩小过滤器是
GL_NEAREST_MIPMAP_LINEAR
。 Your texture is not mipmap complete, so texturing will not work in this mode. 您的纹理不是mipmap完整的,因此纹理化在此模式下将不起作用。 You should set
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
您应该设置
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
(or GL_LINEAR
). (或
GL_LINEAR
)。
You also seem to try to set the texture maginification filter here: 您似乎还尝试在此处设置纹理放大滤镜:
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_REPEAT);
butt GL_REPEAT
is not a valid filter mode at all. 对接
GL_REPEAT
根本不是有效的过滤器模式。
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