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PODrawing with with blur effect on image using opengl
 

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  1. PODrawing with with blur effect on image using opengl
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    <p>I have the same requirement as <a href="https://stackoverflow.com/questions/6980402/blur-effect-wet-in-wet-effect-in-paint-application-using-opengl-es">this question</a> </p> <p>I am right now at situation where i set UIImage on my opengl view. Below is the complete code i used to set uiimage. Also it includes the drawing code. Using below code I am able to set image and drawing on it.</p> <p>when i do not set image in background it allows me to draw blur and smooth drawing</p> <p>but if i set background image it draws solid drawing </p> <p>I want smooth drawing on background image. </p> <p>I have used some of GLPaint code of apple for drawing.</p> <pre><code> - (id)initWithCoder:(NSCoder*)coder { CGImageRef brushImage; CGContextRef brushContext; GLubyte *brushData; size_t width, height; if ((self = [super initWithCoder:coder])) { CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer; eaglLayer.opaque = NO; eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil]; _context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1]; if (!_context || ![EAGLContext setCurrentContext:_context]) { return nil; } { brushImage = [UIImage imageNamed:@"Brush.png"].CGImage; width = CGImageGetWidth(brushImage); height = CGImageGetHeight(brushImage); if(brushImage) { brushData = (GLubyte *) calloc(width * height * 4, sizeof(GLubyte)); brushContext = CGBitmapContextCreate(brushData, width, width, 8, width * 4, CGImageGetColorSpace(brushImage), kCGImageAlphaPremultipliedLast); CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); CGContextDrawImage(brushContext, CGRectMake(0.0, 0.0, (CGFloat)width, (CGFloat)height), brushImage); CGContextRelease(brushContext); glGenTextures(1, &amp;brushTexture); glBindTexture(GL_TEXTURE_2D, brushTexture); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, brushData); free(brushData); } } // Setup OpenGL states glMatrixMode(GL_PROJECTION); CGRect frame = self.bounds; glOrthof(0, frame.size.width, 0, frame.size.height, -1, 1); glViewport(0, 0, frame.size.width , frame.size.height); glMatrixMode(GL_MODELVIEW); glDisable(GL_DITHER); glEnable(GL_TEXTURE_2D); glEnableClientState(GL_VERTEX_ARRAY); glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_POINT_SPRITE_OES); glTexEnvf(GL_POINT_SPRITE_OES, GL_COORD_REPLACE_OES, GL_TRUE); glPointSize(10); } return self; } - (void)layoutSubviews { [EAGLContext setCurrentContext:_context]; [self destroyFramebuffer]; [self createFramebuffer]; if (texture) { [self _updateContent]; glDeleteTextures(1, &amp;texture); texture = 0; } } - (void)_updateContent { NSUInteger width = self.frame.size.width; NSUInteger height = self.frame.size.height; CGFloat texWidth = (1.0 * width)/TEX_SIZE; CGFloat texHeight = (1.0 * height)/TEX_SIZE; GLfloat verts[12] = { 0, height, width, height, width, 0, 0, height, 0, 0, width, 0 }; GLfloat txcoord[12] = { 0, texHeight, texWidth, texHeight, texWidth, 0, 0, texHeight, 0, 0, texWidth, 0 }; [EAGLContext setCurrentContext:_context]; glBindFramebufferOES(GL_FRAMEBUFFER_OES, _viewFramebuffer); glVertexPointer(2, GL_FLOAT, 0, verts); glTexCoordPointer(2, GL_FLOAT, 0, txcoord); glDrawArrays(GL_TRIANGLES, 0, 6); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glBindRenderbufferOES(GL_RENDERBUFFER_OES, _viewRenderbuffer); [_context presentRenderbuffer:GL_RENDERBUFFER_OES]; glDisable(GL_TEXTURE_2D); glDisable(GL_BLEND); } - (void)setContent:(UIImage*)image { if (image) { // self.isNotEmpty = YES; CGImageRef contentImage = image.CGImage; [EAGLContext setCurrentContext:_context]; CGFloat w = CGImageGetWidth(contentImage); CGFloat h = CGImageGetHeight(contentImage); GLubyte *data = (GLubyte *)calloc(TEX_SIZE * TEX_SIZE * 4, sizeof(GLubyte)); CGContextRef ctx = CGBitmapContextCreate(data, TEX_SIZE, TEX_SIZE, 8, TEX_SIZE * 4, CGImageGetColorSpace(contentImage), kCGImageAlphaPremultipliedLast); CGContextScaleCTM(ctx, 1, -1); CGContextTranslateCTM(ctx, 0, -TEX_SIZE); CGContextDrawImage(ctx, CGRectMake(0, 0, w, h), contentImage); CGContextRelease(ctx); if (!texture) { glGenTextures(1, &amp;texture); } glBindTexture(GL_TEXTURE_2D, texture); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TEX_SIZE, TEX_SIZE, 0, GL_RGBA, GL_UNSIGNED_BYTE, data); free(data); } [self setNeedsLayout]; glDisable(GL_VERTEX_ARRAY); } </code></pre> <p>//Called on touchedMoved</p> <pre><code>- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end { glEnable(GL_BLEND); if(1){ sharedDelegate = [AppDelegate appDelegate]; static GLfloat* vertexBuffer = NULL; static NSUInteger vertexMax = 64; NSUInteger vertexCount = 0, count, i; GLenum err; glColor4f(1.0, 0.0, 1.0, 1.0); // Convert locations from Points to Pixels CGFloat scale = self.contentScaleFactor; start.x *= scale; start.y *= scale; end.x *= scale; end.y *= scale; // Allocate vertex array buffer if(vertexBuffer == NULL) vertexBuffer = malloc(vertexMax * 2 * sizeof(GLfloat)); // Add points to the buffer so there are drawing points every X pixels count = MAX(ceilf(sqrtf((end.x - start.x) * (end.x - start.x) + (end.y - start.y) * (end.y - start.y)) / kBrushPixelStep), 1); for(i = 0; i &lt; count; ++i) { if(vertexCount == vertexMax) { vertexMax = 2 * vertexMax; vertexBuffer = realloc(vertexBuffer, vertexMax * 2 * sizeof(GLfloat)); } vertexBuffer[2 * vertexCount + 0] = start.x + (end.x - start.x) * ((GLfloat)i / (GLfloat)count); vertexBuffer[2 * vertexCount + 1] = start.y + (end.y - start.y) * ((GLfloat)i / (GLfloat)count); vertexCount += 1; } if(sharedDelegate.boolIsEraser) { glColor4f(1.0, 1.0, 1.0, 0.5); glBlendFunc( GL_ZERO, GL_ONE_MINUS_SRC_ALPHA); } // Render the vertex array glVertexPointer(2, GL_FLOAT, 0, vertexBuffer); glDrawArrays(GL_POINTS, 0, vertexCount); if(sharedDelegate.boolIsEraser){ // at last restore the mixed-mode glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); } glBindRenderbufferOES(GL_RENDERBUFFER_OES, _viewRenderbuffer); [_context presentRenderbuffer:GL_RENDERBUFFER_OES]; err = glGetError(); if (err != GL_NO_ERROR) NSLog(@"Error in frame. glError: 0x%04X", err); } } </code></pre> <p>Any workaround to accomplish this? I am almost there to my goal but badly stuck here.Any help will be appreciated.</p>
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