用openGLES实现一个画板功能,除了能实现实时涂鸦之外,还要实现动态改变线条颜色,线条宽度,自由绘制圆形矩形等形状,还要实现橡皮擦,撤回上一步操作,清理画板等功能...
图片是以前截的：
iOS:可自由选择各种颜色,宽度,带橡皮擦,可撤回操作的画板涂鸦工具
image
这里是提供几种常用颜色供选择,此外还提供了颜色选择器,可自由选择线条颜色
自由选择线条颜色
首先是初始化openGL
设置layer
- (void)setupLayer{
CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer;
// CALayer 默认是透明的，必须将它设为不透明才能让其可见
eaglLayer.opaque = YES;
// 设置描绘属性，在这里设置不维持渲染内容以及颜色格式为 RGBA8
eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];
//设置放大倍数
[self setContentScaleFactor:[[UIScreen mainScreen] scale]];}
设置上下文
- (void)setupContext{
// 指定 OpenGL 渲染 API 的版本，在这里我们使用 OpenGL ES 2.0
_context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
// 设置为当前上下文
if (!_context || ![EAGLContext setCurrentContext:_context]) {
NSLog(@"Failed to initialize OpenGLES 2.0 context");
exit(1);
}}
设置缓冲区
- (void)setupBuffer{
glDeleteFramebuffers(1, &_viewFramebuffer);
_viewRenderbuffer = 0;
glDeleteRenderbuffers(1, &_viewRenderbuffer);
_viewRenderbuffer = 0;
glGenFramebuffers(1, &_viewFramebuffer);
glGenRenderbuffers(1, &_viewRenderbuffer);
// 设置为当前 framebuffer
glBindFramebuffer(GL_FRAMEBUFFER, _viewFramebuffer);
glBindRenderbuffer(GL_RENDERBUFFER, _viewRenderbuffer);
// 为 颜色缓冲区 分配存储空间
[_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:(id<EAGLDrawable>)self.layer];
// 将 _colorRenderBuffer 装配到 GL_COLOR_ATTACHMENT0 这个装配点上
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _viewRenderbuffer);
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &_backingWidth);
glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &_backingHeight);}
渲染
- (BOOL)render{
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
{
NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
return NO;
}
// Setup the view port in Pixels
glViewport(0, 0, _backingWidth, _backingHeight);
// Create a Vertex Buffer Object to hold our data
glGenBuffers(1, &_vboId);
// Load the brush texture
_brushTexture = [self textureFromName:@"Particle.png"];
// Load shaders
[self setupShaders];
// Enable blending and set a blending function appropriate for premultiplied alpha pixel data
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
return YES;}
设置着色器
- (void)setupShaders{
for (int i = 0; i < NUM_PROGRAMS; i++)
{
char *vsrc = readFile(pathForResource(program[i].vert));
char *fsrc = readFile(pathForResource(program[i].frag));
GLsizei attribCt = 0;
GLchar *attribUsed[NUM_ATTRIBS];
GLint attrib[NUM_ATTRIBS];
GLchar *attribName[NUM_ATTRIBS] = {
"inVertex",
};
const GLchar *uniformName[NUM_UNIFORMS] = {
"MVP", "pointSize", "vertexColor", "texture",
};
// auto-assign known attribs
for (int j = 0; j < NUM_ATTRIBS; j++)
{
if (strstr(vsrc, attribName[j]))
{
attrib[attribCt] = j;
attribUsed[attribCt++] = attribName[j];
}
}
glueCreateProgram(vsrc, fsrc,
attribCt, (const GLchar **)&attribUsed[0], attrib,
NUM_UNIFORMS, &uniformName[0], program[i].uniform,
&program[i].id);
free(vsrc);
free(fsrc);
// Set constant/initalize uniforms
if (i == PROGRAM_POINT)
{
glUseProgram(program[PROGRAM_POINT].id);
// the brush texture will be bound to texture unit 0
glUniform1i(program[PROGRAM_POINT].uniform[UNIFORM_TEXTURE], 0);
// viewing matrices
GLKMatrix4 projectionMatrix = GLKMatrix4MakeOrtho(0, _backingWidth, 0, _backingHeight, -1, 1);
GLKMatrix4 modelViewMatrix = GLKMatrix4Identity; // this sample uses a constant identity modelView matrix
GLKMatrix4 MVPMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix);
glUniformMatrix4fv(program[PROGRAM_POINT].uniform[UNIFORM_MVP], 1, GL_FALSE, MVPMatrix.m);
// point size
glUniform1f(program[PROGRAM_POINT].uniform[UNIFORM_POINT_SIZE], _brushTexture.width / 12 * self.lineWidthBlock());
// initialize brush color
glUniform4fv(program[PROGRAM_POINT].uniform[UNIFORM_VERTEX_COLOR], 1, _brushColor);
}
}
glError();}
设置纹理
- (textureInfo_t)textureFromName:(NSString *)name{
CGImageRef brushImage;
CGContextRef brushContext;
GLubyte *brushData;
size_t width, height;
GLuint texId;
textureInfo_t texture;
// 1获取图片的CGImageRef
brushImage = [UIImage imageNamed:name].CGImage;
// 2 读取图片的大小
width = CGImageGetWidth(brushImage);
height = CGImageGetHeight(brushImage);
// Allocate memory needed for the bitmap context
brushData = (GLubyte *) calloc(width * height * 4, sizeof(GLubyte));
// Use the bitmatp creation function provided by the Core Graphics framework.
brushContext = CGBitmapContextCreate(brushData, width, height, 8, width * 4, CGImageGetColorSpace(brushImage), kCGImageAlphaPremultipliedLast);
// 3在CGContextRef上绘图
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, &texId);
// 4绑定纹理到默认的纹理ID（这里只有一张图片，故而相当于默认于片元着色器里面的colorMap，如果有多张图不可以这么做）
glBindTexture(GL_TEXTURE_2D, texId);
// 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);
// Specify a 2D texture image, providing the a pointer to the image data in memory
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, (int)width, (int)height, 0, GL_RGBA, GL_UNSIGNED_BYTE, brushData);
// Release the image data; it's no longer needed
free(brushData);
texture.id = texId;
texture.width = (int)width;
texture.height = (int)height;
return texture;}
画线部分代码
- (NSInteger)readyRenderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end{
static GLfloat* vertexBuffer = NULL;
static NSUInteger vertexMax = 64;
NSUInteger vertexCount = 0,
count,
i;
// 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 < 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;
}
// Load data to the Vertex Buffer Object
glBindBuffer(GL_ARRAY_BUFFER, _vboId);
glBufferData(GL_ARRAY_BUFFER, vertexCount*2*sizeof(GLfloat), vertexBuffer, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(ATTRIB_VERTEX);
glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, 0);
// Draw
glUseProgram(program[PROGRAM_POINT].id);
glDrawArrays(GL_POINTS, 0, (int)vertexCount);
return vertexCount;}
矩形绘制就是四条直线：
- (NSInteger)readyRenderRectangleFromPoint:(CGPoint)start toPoint:(CGPoint)end{
CGPoint point2 = CGPointMake(start.x, end.y);
CGPoint point3 = CGPointMake(end.x, start.y);
NSInteger totalCount = 0;
totalCount += [self readyRenderLineFromPoint:start toPoint:point2];
totalCount += [self readyRenderLineFromPoint:point2 toPoint:end];
totalCount += [self readyRenderLineFromPoint:end toPoint:point3];
totalCount += [self readyRenderLineFromPoint:point3 toPoint:start];
return totalCount;}
圆形的绘制将圆切割成100条线去绘制：
- (NSInteger)readyRenderCircularFromPoint:(CGPoint)start toPoint:(CGPoint)end{
GLfloat radius = sqrt(pow((start.x - end.x), 2) + pow((start.y - end.y), 2))/2; //半径
CGPoint center = CGPointMake((start.x + end.x)/2, (start.y + end.y)/2); //圆心
GLfloat pointCount = 100;
GLfloat delta = 2.0*M_PI/pointCount;
NSString * lastPoint = nil;
CGPoint firstPoint = CGPointZero;
CGFloat totalCount = 0;
for (NSInteger i = 0; i < pointCount; i++) {
GLfloat x = radius * cos(delta * i) + center.x;
GLfloat y = radius * sin(delta * i) + center.y;
CGPoint currentPoint = CGPointMake(x, y);
if (i == 0) {
firstPoint = currentPoint;
}
if (lastPoint != nil) {
totalCount += [self readyRenderLineFromPoint:CGPointFromString(lastPoint) toPoint:currentPoint];
}
lastPoint = NSStringFromCGPoint(currentPoint);
if (i == pointCount - 1) {
totalCount += [self readyRenderLineFromPoint:CGPointFromString(lastPoint) toPoint:firstPoint];
}
}
return totalCount;}
绘制的时候则是根据每次操作的画笔类型去绘制：
- (void)showLines{
[EAGLContext setCurrentContext:_context];
glBindFramebuffer(GL_FRAMEBUFFER, _viewFramebuffer);
glClearColor(0.0, 0.0, 0.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT);
NSInteger totalCount = 0;
for (NSInteger i = 0; i < self.pointsArray.count; i++) {
DrawModel * model = self.pointsArray[i];
UIColor * currentColor = model.lineColor;
[self setBrushColorWithRed:[currentColor.RGBArray[0] floatValue] green:[currentColor.RGBArray[1] floatValue] blue:[currentColor.RGBArray[2] floatValue] alpha:[currentColor.RGBArray[3] floatValue]];
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
// point size
glUniform1f(program[PROGRAM_POINT].uniform[UNIFORM_POINT_SIZE], _brushTexture.width / 12 * model.lineWidth);
if (model.isEraser) {
[self setIsEraser:model.isEraser];
}
if (model.pointsArray.count >= 2) {
if (model.penType == kDrawPenTypeCurve || model.isEraser) {
for (NSInteger j = 0; j < model.pointsArray.count - 1; j++) {
DrawPointModel * pointModel1 = model.pointsArray[j];
DrawPointModel * pointModel2 = model.pointsArray[j + 1];
CGPoint start = CGPointMake(pointModel1.x, pointModel1.y);
CGPoint end = CGPointMake(pointModel2.x, pointModel2.y);
totalCount += [self readyRenderLineFromPoint:start toPoint:end];
}
}else{
DrawPointModel * pointModel1 = model.pointsArray.firstObject;
DrawPointModel * pointModel2 = model.pointsArray.lastObject;
CGPoint start = CGPointMake(pointModel1.x, pointModel1.y);
CGPoint end = CGPointMake(pointModel2.x, pointModel2.y);
switch (model.penType) {
case kDrawPenTypeStraight:
{
totalCount += [self readyRenderLineFromPoint:start toPoint:end];
}
break;
case kDrawPenTypeRectangle:
{
totalCount += [self readyRenderRectangleFromPoint:start toPoint:end];
}
break;
case kDrawPenTypeCircular:
{
totalCount += [self readyRenderCircularFromPoint:start toPoint:end];
}
break;
default:
break;
}
}
}
}
// Display the buffer
glBindRenderbuffer(GL_RENDERBUFFER, _viewRenderbuffer);
[_context presentRenderbuffer:GL_RENDERBUFFER];
NSLog(@"totalCount: %zd",totalCount);}
然后是撤销，则是将上次操作的所有point移除,并重新绘制,此处的showLines就是将所有点重新绘制一遍
- (void)undo{
if (!self.pointsArray.count) return;
[self.pointsArray removeLastObject];
[self showLines];}
橡皮擦则是修改下颜色以及绘制模式
- (void)setIsEraser:(BOOL)isEraser{
if (isEraser) {
[self setBrushColorWithRed:0 green:0 blue:0 alpha:0];
// 设置绘画模式
glBlendFunc(GL_ONE, GL_ZERO);
}else{
UIColor * currentColor = self.lineColorBlock();
[self setBrushColorWithRed:[currentColor.RGBArray[0] floatValue] green:[currentColor.RGBArray[1] floatValue] blue:[currentColor.RGBArray[2] floatValue] alpha:[currentColor.RGBArray[3] floatValue]];
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
}}
效果图如下：
多种形状的绘制
具体操作逻辑细节和UI等是参考微信的图片编辑中的画板
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