paintingview.m

一个可以演示OpenGL在xcode里的画点的程序

/*

File: PaintingView.m
Abstract: The class responsible for the finger painting.

Version: 1.6

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*/

#import "PaintingView.h"

//CLASS IMPLEMENTATIONS:

@implementation PaintingView

@synthesize  location;
@synthesize  previousLocation;

- (id) initWithFrame:(CGRect)frame
{
	NSMutableArray*	recordedPaths;
	CGImageRef		brushImage;
	CGContextRef	brushContext;
	GLubyte			*brushData;
	size_t			width, height;
	
	if((self = [super initWithFrame:frame pixelFormat:GL_RGB565_OES depthFormat:0 preserveBackbuffer:YES])) {
		[self setCurrentContext];

		// Create a texture from an image
		// First create a UIImage object from the data in a image file, and then extract the Core Graphics image
		brushImage = [UIImage imageNamed:@"Particle.png"].CGImage;
		
		// Get the width and height of the image
		width = CGImageGetWidth(brushImage);
		height = CGImageGetHeight(brushImage);
		
		// Texture dimensions must be a power of 2. If you write an application that allows users to supply an image,
		// you'll want to add code that checks the dimensions and takes appropriate action if they are not a power of 2.
		
		// Make sure the image exists
		if(brushImage) {
			// Allocate  memory needed for the bitmap context
			brushData = (GLubyte *) malloc(width * height * 4);
			// Use  the bitmatp creation function provided by the Core Graphics framework. 
			brushContext = CGBitmapContextCreate(brushData, width, width, 8, width * 4, CGImageGetColorSpace(brushImage), kCGImageAlphaPremultipliedLast);
			// After you create the context, you can draw the  image to the context.
			CGContextDrawImage(brushContext, CGRectMake(0.0, 0.0, (CGFloat)width, (CGFloat)height), brushImage);
			// You don't need the context at this point, so you need to release it to avoid memory leaks.
			CGContextRelease(brushContext);
			// Use OpenGL ES to generate a name for the texture.
			glGenTextures(1, &brushTexture);
			// Bind the texture name. 
			glBindTexture(GL_TEXTURE_2D, brushTexture);
			// Specify a 2D texture image, providing the a pointer to the image data in memory
			glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, brushData);
			// Release  the image data; it's no longer needed
            free(brushData);		
			// Set the texture parameters to use a minifying filter and a linear filer (weighted average)
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
			
			// Enable use of the texture
			glEnable(GL_TEXTURE_2D);
			// Set a blending function to use
			glBlendFunc(GL_SRC_ALPHA, GL_ONE);
			// Enable blending
			glEnable(GL_BLEND);
		}
		
		//Set up OpenGL states
		glDisable(GL_DITHER);
		glMatrixMode(GL_PROJECTION);
		glOrthof(0, frame.size.width, 0, frame.size.height, -1, 1);
		glMatrixMode(GL_MODELVIEW);
		glEnable(GL_TEXTURE_2D);
		glEnableClientState(GL_VERTEX_ARRAY);
	    glEnable(GL_BLEND);
		glBlendFunc(GL_SRC_ALPHA, GL_ONE);
		glEnable(GL_POINT_SPRITE_OES);
		glTexEnvf(GL_POINT_SPRITE_OES, GL_COORD_REPLACE_OES, GL_TRUE);
		glPointSize(width / kBrushScale);
			
		//Make sure to start with a cleared buffer
		[self erase];
		
		//Playback recorded path, which is "Shake Me"
		recordedPaths = [NSMutableArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"Recording" ofType:@"data"]];
		if([recordedPaths count])
			[self performSelector:@selector(playback:) withObject:recordedPaths afterDelay:0.2];
		
	}
	
	return self;
}

// Releases resources when they are not longer needed.
- (void) dealloc
{
		
	glDeleteFramebuffersOES(1, &drawingFramebuffer);
	glDeleteTextures(1, &drawingTexture);

	[super dealloc];
}

// Erases the screen
- (void) erase
{
	//Clear the buffer
	glClear(GL_COLOR_BUFFER_BIT);
	
	//Display the buffer
	[self swapBuffers];
}


// Drawings a line onscreen based on where the user touches
- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end
{
	static GLfloat*		vertexBuffer = NULL;
	static NSUInteger	vertexMax = 64;
	NSUInteger			vertexCount = 0,
						count,
						i;
	
	//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 < 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;
	}
	
	//Render the vertex array
	glVertexPointer(2, GL_FLOAT, 0, vertexBuffer);
	glDrawArrays(GL_POINTS, 0, vertexCount);
	
	// Display the buffer
	[self swapBuffers];
}

// Reads previously recorded points and draws them onscreen. This is the Shake Me message that appears when the application launches.
- (void) playback:(NSMutableArray*)recordedPaths
{
	NSData*				data = [recordedPaths objectAtIndex:0];
	CGPoint*			point = (CGPoint*)[data bytes];
	NSUInteger			count = [data length] / sizeof(CGPoint),
						i;
	
	//Render the current path
	for(i = 0; i < count - 1; ++i, ++point)
		[self renderLineFromPoint:*point toPoint:*(point + 1)];
	
	//Render the next path after a short delay 
	[recordedPaths removeObjectAtIndex:0];
	if([recordedPaths count])
		[self performSelector:@selector(playback:) withObject:recordedPaths afterDelay:0.01];
}



// Handles the start of a touch
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
	CGRect				bounds = [self bounds];
    UITouch*	touch = [[event touchesForView:self] anyObject];
	firstTouch = YES;
	//Convert touch point from UIView referential to OpenGL one (upside-down flip)
	location = [touch locationInView:self];
	location.y = bounds.size.height - location.y;
}

// Handles the continuation of a touch.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{  
   	  
	CGRect				bounds = [self bounds];
	UITouch*			touch = [[event touchesForView:self] anyObject];
		
	//Convert touch point from UIView referential to OpenGL one (upside-down flip)
	if (firstTouch) {
		firstTouch = NO;
		previousLocation = [touch previousLocationInView:self];
		previousLocation.y = bounds.size.height - previousLocation.y;
	} else {
		location = [touch locationInView:self];
	    location.y = bounds.size.height - location.y;
		previousLocation = [touch previousLocationInView:self];
		previousLocation.y = bounds.size.height - previousLocation.y;
	}
		
	// Render the stroke
	[self renderLineFromPoint:previousLocation toPoint:location];
	
	
}

// Handles the end of a touch event when the touch is a tap.
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
	CGRect				bounds = [self bounds];
    UITouch*	touch = [[event touchesForView:self] anyObject];
	if (firstTouch) {
		firstTouch = NO;
		previousLocation = [touch previousLocationInView:self];
		previousLocation.y = bounds.size.height - previousLocation.y;
		[self renderLineFromPoint:previousLocation toPoint:location];
	}

}

// Handles the end of a touch event.
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
	// If appropriate, add code necessary to save the state of the application.
	// This application is not saving state.
}

@end