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我想爲程序添加一些後期處理功能。渲染是使用openGL完成的。我只想讓程序加載一些自制的片段着色器,並在視頻流上使用它們。紋理上的片段着色器
我寫了一段使用「OpenGL Shader Builder」的着色器,它只是在灰度變成紋理。着色器在着色器構建器中運行良好,但我無法在主程序中使用它。屏幕全黑。
下面是設置:
@implementation PluginGLView
- (id) initWithCoder: (NSCoder *) coder
{
const GLubyte * strExt;
if ((self = [super initWithCoder:coder]) == nil)
return nil;
glLock = [[NSLock alloc] init];
if (nil == glLock) {
[self release];
return nil;
}
// Init pixel format attribs
NSOpenGLPixelFormatAttribute attrs[] =
{
NSOpenGLPFAAccelerated,
NSOpenGLPFANoRecovery,
NSOpenGLPFADoubleBuffer,
0
};
// Get pixel format from OpenGL
NSOpenGLPixelFormat* pixFmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs];
if (!pixFmt)
{
NSLog(@"No Accelerated OpenGL pixel format found\n");
NSOpenGLPixelFormatAttribute attrs2[] =
{
NSOpenGLPFANoRecovery,
0
};
// Get pixel format from OpenGL
pixFmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs2];
if (!pixFmt) {
NSLog(@"No OpenGL pixel format found!\n");
[self release];
return nil;
}
}
[self setPixelFormat:[pixFmt autorelease]];
/*
long swapInterval = 1 ;
[[self openGLContext]
setValues:&swapInterval
forParameter:NSOpenGLCPSwapInterval];
*/
[glLock lock];
[[self openGLContext] makeCurrentContext];
// Init object members
strExt = glGetString (GL_EXTENSIONS);
texture_range = gluCheckExtension ((const unsigned char *)"GL_APPLE_texture_range", strExt) ? GL_TRUE : GL_FALSE;
texture_hint = GL_STORAGE_SHARED_APPLE ;
client_storage = gluCheckExtension ((const unsigned char *)"GL_APPLE_client_storage", strExt) ? GL_TRUE : GL_FALSE;
rect_texture = gluCheckExtension((const unsigned char *)"GL_EXT_texture_rectangle", strExt) ? GL_TRUE : GL_FALSE;
// Setup some basic OpenGL stuff
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// Loads the shaders
shader=LoadShader(GL_FRAGMENT_SHADER,"/Users/alexandremathieu/fragment.fs");
program=glCreateProgram();
glAttachShader(program, shader);
glLinkProgram(program);
glUseProgram(program);
[NSOpenGLContext clearCurrentContext];
[glLock unlock];
image_width = 1024;
image_height = 512;
image_depth = 16;
image_type = GL_UNSIGNED_SHORT_1_5_5_5_REV;
image_base = (GLubyte *) calloc(((IMAGE_COUNT * image_width * image_height)/3) * 4, image_depth >> 3);
if (image_base == nil) {
[self release];
return nil;
}
// Create and load textures for the first time
[self loadTextures:GL_TRUE];
// Init fps timer
//gettimeofday(&cycle_time, NULL);
drawBG = YES;
// Call for a redisplay
noDisplay = YES;
PSXDisplay.Disabled = 1;
[self setNeedsDisplay:true];
return self;
}
這裏是「渲染畫面」功能至極基本呈現...屏幕。
- (void)renderScreen
{
int bufferIndex = whichImage;
glBindTexture(GL_TEXTURE_RECTANGLE_EXT, bufferIndex+1);
glUseProgram(program);
int loc=glGetUniformLocation(program, "texture");
glUniform1i(loc,bufferIndex+1);
glTexSubImage2D(GL_TEXTURE_RECTANGLE_EXT, 0, 0, 0, image_width, image_height, GL_BGRA, image_type, image[bufferIndex]);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f);
glVertex2f(-1.0f, 1.0f);
glTexCoord2f(0.0f, image_height);
glVertex2f(-1.0f, -1.0f);
glTexCoord2f(image_width, image_height);
glVertex2f(1.0f, -1.0f);
glTexCoord2f(image_width, 0.0f);
glVertex2f(1.0f, 1.0f);
glEnd();
[[self openGLContext] flushBuffer];
[NSOpenGLContext clearCurrentContext];
//[glLock unlock];
}
最後這裏是着色器。
uniform sampler2DRect texture;
void main() {
vec4 color, texel;
color = gl_Color;
texel = texture2DRect(texture, gl_TexCoord[0].xy);
color *= texel;
// Begin Shader
float gray=0.0;
gray+=(color.r + color.g + color.b)/3.0;
color=vec4(gray,gray,gray,color.a);
// End Shader
gl_FragColor = color;
}
裝載和使用着色器的工作,因爲我能夠把屏幕上的所有紅色與此着色器
void main(){
gl_FragColor=vec4(1.0,0.0,0.0,1.0);
}
如果着色器包含一個語法錯誤,我從LoadShader功能的錯誤信息等等。如果我刪除了着色器的使用,一切正常。
我認爲問題來自「將紋理作爲統一參數傳遞」的問題。但這些都是我對openGL的第一步,我無法確定任何事情。
不要猶豫,要求更多的信息。
謝謝堆棧O.
我會研究亮度以生成好的灰度圖像:http://en.wikipedia.org/wiki/Luma_%28video%29 – Luca 2010-03-15 06:46:47