[英]How can I render an RGB bitmap into a GLKView using 2D textures?
我有一個內存中的“位圖”,它只是一個malloced Byte *
數組,它包含一個簡單RGB格式的像素數據(所以字節數組的大小是3 *像素數)。
我的應用程序只是一個帶有GLKView
實例的視圖控制器。 我已經像這樣實現了它的委托:
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
}
並且正如預期的那樣,它設置了GLKView的背景顏色。
我現在要做的是為glkView:drawInRect:
這個實現添加代碼glkView:drawInRect:
這樣我的“位圖”就會呈現在這個GLKView中。 但我似乎無法找到任何簡單的方法; 我對OpenGL可以做的所有不同事情感到不知所措,所有這些都比我在這里嘗試的要復雜得多。
glReadPixels
似乎有點像我在這里,因為它似乎提供了一個指向緩沖區數據的指針。
編輯:顯然這只能通過使用紋理來完成。 我試圖用這個示例代碼實現這一點(請注意,我的“位圖”是每個樣本4個字節,與格式參數匹配):
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// raw data
int width = 30;
int height = 30;
int pixelCount = width * height;
int byteSize = pixelCount * 4;
GLubyte *textureData = (GLubyte *)malloc(byteSize);
for (int i = 0; i < byteSize; i++) {
textureData[i] = 255; // white
}
glEnable(GL_TEXTURE_2D);
GLuint textureID;
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0,
GL_RGBA, GL_UNSIGNED_BYTE, textureData);
free(textureData);
}
...... 但它不起作用 。 glClear()
調用按預期工作,並將整個背景設置為紅色; 但如果我正確理解紋理樣本,下面的代碼應該在角落里繪制一個30x30的白色方塊,但我得到的只是純紅色背景。
誰能發現我在這里做錯了什么?
抱歉推進OpenGL :)
我會創建CGImage
然后創建UIImage
void *baseAddress = & textureData;
size_t bytesPerRow = width * 4;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGImageRef cgImage = CGBitmapContextCreateImage(context);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
UIImage *image = [UIImage imageWithCGImage:cgImage];
然后使用drawInRect繪制它:
這是我寫的代碼。 這不是生產代碼:它缺乏對openGL錯誤的檢查,一些小的泄漏以及全局變量,但它是增強它的好地方。
#import "ViewController.h"
#include <OpenGLES/ES2/gl.h>
#include <OpenGLES/ES2/glext.h>
@interface ViewController ()
@end
@implementation ViewController
GLuint tex;
float vertices[] = {
// Position Texcoords
-1.0f, 1.0f, 0.0f, 0.0f, // Top-left
1.0f, 1.0f, 1.0f, 0.0f, // Top-right
1.0f, -1.0f, 1.0f, 1.0f, // Bottom-right
-1.0, -1.0f, 0.0f, 1.0f // Bottom-left
};
const char * vertexShader = "attribute vec2 position;\n"
"attribute vec2 TexCoordIn;\n"
"varying vec2 TexCoordOut;\n"
"void main() {\n"
"gl_Position = vec4(position, 0.0, 1.0);\n"
"TexCoordOut = TexCoordIn;\n"
"}\n";
const char * fragmentShader = "precision mediump float;\n"
"varying lowp vec2 TexCoordOut;\n"
"uniform sampler2D Texture;\n"
"void main() {\n"
"gl_FragColor = texture2D(Texture, TexCoordOut);\n"
"}\n";
GLuint shaderProgram;
GLuint vao;
GLuint vbo;
-(void) initOpenGLObjects {
glGenVertexArraysOES(1, &vao);
glBindVertexArrayOES(vao);
glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
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);
glGenerateMipmap(GL_TEXTURE_2D);
GLuint vs = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vs, 1, &vertexShader, NULL);
glCompileShader(vs);
GLint status;
glGetShaderiv(vs, GL_COMPILE_STATUS, &status);
char buffer[512];
glGetShaderInfoLog(vs, 512, NULL, buffer);
GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fs, 1, &fragmentShader, NULL);
glCompileShader(fs);
glGetShaderiv(fs, GL_COMPILE_STATUS, &status);
glGetShaderInfoLog(fs, 512, NULL, buffer);
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vs);
glAttachShader(shaderProgram, fs);
glLinkProgram(shaderProgram);
GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
GLint texAttrib = glGetAttribLocation(shaderProgram, "TexCoordIn");
glGenBuffers(1, &vbo); // Generate 1 buffer
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 4*sizeof(float), 0);
glVertexAttribPointer(texAttrib, 2, GL_FLOAT, GL_FALSE, 4*sizeof(float), (void*)(2*sizeof(float)));
glEnableVertexAttribArray(posAttrib);
glEnableVertexAttribArray(texAttrib);
}
-(void) viewDidLoad{
[super viewDidLoad];
self.glkView.context = [[EAGLContext alloc] initWithAPI:
kEAGLRenderingAPIOpenGLES2];
[EAGLContext setCurrentContext:self.glkView.context];
CADisplayLink *displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(update)];
[displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
self.glkView.delegate = self;
[self initOpenGLObjects];
}
- (void)update
{
[self.glkView setNeedsDisplay];
}
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
int width = 300;
int height = 300;
int pixelCount = width * height;
int byteSize = pixelCount * 4;
GLubyte *textureData = (GLubyte *)malloc(byteSize);
static int time = 0;
time = (time+1)%256;
for (int i = 0; i < byteSize; i+=4) {
textureData[i] = 255;
textureData[i+1] = time;
textureData[i+2] = 255;
textureData[i+3] = 255;
}
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0,
GL_RGBA, GL_UNSIGNED_BYTE, textureData);
glUseProgram(shaderProgram);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
free(textureData);
}
@end
我不知道你想如何更新數據,也許你不必每次都使用malloc / free,只需做一些小改動並用glTexSubImage2D
更新它。 大部分時間都花在填充數據上。
這段代碼在我的MacBook上運行,Xcode 7采用模擬器,iPhone 6采用iOS 9.0.2。
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