手写签字并保存图片
网上找了点现成的代码,又自己改了下...(前人方法)

首先新建一个PPSSignatureView继承GLKView

然后再使用的时候,创建一个继承GLKViewController的控制器,这里是关键,避免入坑,UIView addSubView的时候, glkView是无法显示的...

简单说,代码如下:

.h文件

#import <UIKit/UIKit.h>
#import <GLKit/GLKit.h>

@interface PPSSignatureView : GLKView
@property (nonatomic, strong) GLKBaseEffect *effect;
@property (nonatomic, assign) CGFloat colorR;
@property (nonatomic, assign) CGFloat colorG;
@property (nonatomic, assign) CGFloat colorB;
@property (nonatomic, assign) CGFloat alpha;
@property (nonatomic, assign) float maxFontSize;
@property (assign, nonatomic) UIColor *strokeColor;
@property (assign, nonatomic) BOOL hasSignature;
@property (strong, nonatomic) UIImage *signatureImage;
@property (nonatomic, strong) NSMutableArray *pointMArray;
/** 清除所有线条*/
- (void)erase;
@end

.m文件

#import "PPSSignatureView.h"
#import <OpenGLES/ES2/glext.h>

#define             STROKE_WIDTH_MIN 0.004 // Stroke width determined by touch velocity
#define       STROKE_WIDTH_SMOOTHING 0.3   // Low pass filter alpha

#define           VELOCITY_CLAMP_MIN 20
#define           VELOCITY_CLAMP_MAX 5000

#define QUADRATIC_DISTANCE_TOLERANCE 3.0   // Minimum distance to make a curve

#define             MAXIMUM_VERTECES 100000


static GLKVector3 StrokeColor = { 0, 0, 0 };
static float clearColor[4] = { 1, 1, 1, 0 };

// Vertex structure containing 3D point and color
struct PPSSignaturePoint
{
	GLKVector3		vertex;
	GLKVector3		color;
};
typedef struct PPSSignaturePoint PPSSignaturePoint;


// Maximum verteces in signature
static const int maxLength = MAXIMUM_VERTECES;


// Append vertex to array buffer
static inline void addVertex(uint *length, PPSSignaturePoint v) {
    if ((*length) >= maxLength) {
        return;
    }
    
    GLvoid *data = glMapBufferOES(GL_ARRAY_BUFFER, GL_WRITE_ONLY_OES);
    memcpy(data + sizeof(PPSSignaturePoint) * (*length), &v, sizeof(PPSSignaturePoint));
    glUnmapBufferOES(GL_ARRAY_BUFFER);
    
    (*length)++;
}

static inline CGPoint QuadraticPointInCurve(CGPoint start, CGPoint end, CGPoint controlPoint, float percent) {
    double a = pow((1.0 - percent), 2.0);
    double b = 2.0 * percent * (1.0 - percent);
    double c = pow(percent, 2.0);
    
    return (CGPoint) {
        a * start.x + b * controlPoint.x + c * end.x,
        a * start.y + b * controlPoint.y + c * end.y
    };
}

static float generateRandom(float from, float to) { return random() % 10000 / 10000.0 * (to - from) + from; }
static float clamp(float min, float max, float value) { return fmaxf(min, fminf(max, value)); }


// Find perpendicular vector from two other vectors to compute triangle strip around line
static GLKVector3 perpendicular(PPSSignaturePoint p1, PPSSignaturePoint p2) {
    GLKVector3 ret;
    ret.x = p2.vertex.y - p1.vertex.y;
    ret.y = -1 * (p2.vertex.x - p1.vertex.x);
    ret.z = 0;
    return ret;
}

static PPSSignaturePoint ViewPointToGL(CGPoint viewPoint, CGRect bounds, GLKVector3 color) {

    return (PPSSignaturePoint) {
        {
            (viewPoint.x / bounds.size.width * 2.0 - 1),
            ((viewPoint.y / bounds.size.height) * 2.0 - 1) * -1,
            0
        },
        color
    };
}


@interface PPSSignatureView () {
    // OpenGL state
    EAGLContext *context;
    
    
    GLuint vertexArray;
    GLuint vertexBuffer;
    GLuint dotsArray;
    GLuint dotsBuffer;
    
    
    // Array of verteces, with current length
    PPSSignaturePoint SignatureVertexData[maxLength];
    uint length;
    
    PPSSignaturePoint SignatureDotsData[maxLength];
    uint dotsLength;
    
    
    // Width of line at current and previous vertex
    float penThickness;
    float previousThickness;
    
    
    // Previous points for quadratic bezier computations
    CGPoint previousPoint;
    CGPoint previousMidPoint;
    PPSSignaturePoint previousVertex;
    PPSSignaturePoint currentVelocity;
}

@property (nonatomic, strong) NSMutableArray *drawPointArray;

@end


@implementation PPSSignatureView

- (NSMutableArray *)pointMArray {
    if(nil == _pointMArray) {
        _pointMArray = [NSMutableArray array];
    }
    return _pointMArray;
}

- (void)commonInit {
    context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    
    if (context) {
        time(NULL);
        
        self.backgroundColor = [UIColor whiteColor];
        self.opaque = NO;
        
        self.context = context;
        self.drawableDepthFormat = GLKViewDrawableDepthFormat24;
		self.enableSetNeedsDisplay = YES;
        
        // Turn on antialiasing
        self.drawableMultisample = GLKViewDrawableMultisample4X;
        
        [self setupGL];
        
        // Capture touches
        UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
        pan.maximumNumberOfTouches = pan.minimumNumberOfTouches = 1;
        pan.cancelsTouchesInView = YES;
        [self addGestureRecognizer:pan];
        
        // For dotting your i's
        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)];
        tap.cancelsTouchesInView = YES;
        [self addGestureRecognizer:tap];
 
#warning 这个地方是长按删除的操作
        // Erase with long press
        UILongPressGestureRecognizer *longer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPress:)];
        longer.cancelsTouchesInView = YES;
        [self addGestureRecognizer:longer];
        
    } else [NSException raise:@"NSOpenGLES2ContextException" format:@"Failed to create OpenGL ES2 context"];
}


- (id)initWithCoder:(NSCoder *)aDecoder
{
    if (self = [super initWithCoder:aDecoder]) [self commonInit];
    return self;
}


- (id)initWithFrame:(CGRect)frame context:(EAGLContext *)ctx
{
    if (self = [super initWithFrame:frame context:ctx]) [self commonInit];
    return self;
}


- (void)dealloc
{
    [self tearDownGL];
    
    if ([EAGLContext currentContext] == context) {
        [EAGLContext setCurrentContext:nil];
    }
	context = nil;
}


- (void)drawRect:(CGRect)rect
{
    // 清空当前所有颜色缓存
    glClearColor(clearColor[0], clearColor[1], clearColor[2], clearColor[3]);
    glClear(GL_COLOR_BUFFER_BIT);

    [self.effect prepareToDraw];
    
    // Drawing of signature lines
    if (length > 2) {
        glBindVertexArrayOES(vertexArray);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, length);
    }

    if (dotsLength > 0) {
        glBindVertexArrayOES(dotsArray);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, dotsLength);
    }
}

#warning 清除的操作
- (void)erase {
    length = 0;
    dotsLength = 0;
    self.hasSignature = NO;
	
	[self setNeedsDisplay];
}



- (UIImage *)signatureImage
{
	if (!self.hasSignature)
		return nil;

//    self.hidden = YES;
//
//    self.strokeColor = [UIColor whiteColor];
//    [self setNeedsDisplay];
    UIImage *screenshot = [self snapshot];
    
//    self.strokeColor = nil;
//
//    self.hidden = NO;
    return screenshot;
}


#pragma mark - Gesture Recognizers


- (void)tap:(UITapGestureRecognizer *)t {

    CGPoint l = [t locationInView:self];
    
    if (t.state == UIGestureRecognizerStateRecognized) {
        glBindBuffer(GL_ARRAY_BUFFER, dotsBuffer);
        
        PPSSignaturePoint touchPoint = ViewPointToGL(l, self.bounds, (GLKVector3){1, 1, 1});
        addVertex(&dotsLength, touchPoint);
        
        PPSSignaturePoint centerPoint = touchPoint;
        centerPoint.color = StrokeColor;
        addVertex(&dotsLength, centerPoint);

        static int segments = 20;
        GLKVector2 radius = (GLKVector2){
            clamp(0.00001, 0.02, penThickness * generateRandom(0.5, 1.5)),
            clamp(0.00001, 0.02, penThickness * generateRandom(0.5, 1.5))
        };
        GLKVector2 velocityRadius = radius;
        float angle = 0;
        
        for (int i = 0; i <= segments; i++) {
            
            PPSSignaturePoint p = centerPoint;
            p.vertex.x += velocityRadius.x * cosf(angle);
            p.vertex.y += velocityRadius.y * sinf(angle);
            
            addVertex(&dotsLength, p);
            addVertex(&dotsLength, centerPoint);
            
            angle += M_PI * 2.0 / segments;
        }
               
        addVertex(&dotsLength, touchPoint);
        
        glBindBuffer(GL_ARRAY_BUFFER, 0);
    }
    
    [self setNeedsDisplay];
}


- (void)longPress:(UILongPressGestureRecognizer *)lp {
    [self erase];
}

- (void)pan:(UIPanGestureRecognizer *)p {
    
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    
    CGPoint v = [p velocityInView:self];
    CGPoint l = [p locationInView:self];
    //[self.drawPointArray addObject:];
    
    currentVelocity = ViewPointToGL(v, self.bounds, (GLKVector3){0,0,0});
    float distance = 0.;
    if (previousPoint.x > 0) {
        distance = sqrtf((l.x - previousPoint.x) * (l.x - previousPoint.x) + (l.y - previousPoint.y) * (l.y - previousPoint.y));
    }    

    float velocityMagnitude = sqrtf(v.x*v.x + v.y*v.y);
    float clampedVelocityMagnitude = clamp(VELOCITY_CLAMP_MIN, VELOCITY_CLAMP_MAX, velocityMagnitude);
    float normalizedVelocity = (clampedVelocityMagnitude - VELOCITY_CLAMP_MIN) / (VELOCITY_CLAMP_MAX - VELOCITY_CLAMP_MIN);
    
    float lowPassFilterAlpha = STROKE_WIDTH_SMOOTHING;
    float newThickness = (self.maxFontSize - STROKE_WIDTH_MIN) * (1 - normalizedVelocity) + STROKE_WIDTH_MIN;
    penThickness = penThickness * lowPassFilterAlpha + newThickness * (1 - lowPassFilterAlpha);
    
    if ([p state] == UIGestureRecognizerStateBegan) {
        
        previousPoint = l;
        previousMidPoint = l;
        
        PPSSignaturePoint startPoint = ViewPointToGL(l, self.bounds, (GLKVector3){1, 1, 1});
        previousVertex = startPoint;
        previousThickness = penThickness;
        
        addVertex(&length, startPoint);
        addVertex(&length, previousVertex);
		
		self.hasSignature = YES;
        
    } else if ([p state] == UIGestureRecognizerStateChanged) {
        
        CGPoint mid = CGPointMake((l.x + previousPoint.x) / 2.0, (l.y + previousPoint.y) / 2.0);
        
        if (distance > QUADRATIC_DISTANCE_TOLERANCE) {
            // Plot quadratic bezier instead of line
            unsigned int i;
            
            int segments = (int) distance / 1.5;
            
            float startPenThickness = previousThickness;
            float endPenThickness = penThickness;
            previousThickness = penThickness;
            
            for (i = 0; i < segments; i++)
            {
                penThickness = startPenThickness + ((endPenThickness - startPenThickness) / segments) * i;
                
                CGPoint quadPoint = QuadraticPointInCurve(previousMidPoint, mid, previousPoint, (float)i / (float)(segments));
                
                PPSSignaturePoint v = ViewPointToGL(quadPoint, self.bounds, StrokeColor);
                [self addTriangleStripPointsForPrevious:previousVertex next:v];
                
                previousVertex = v;
            }
        } else if (distance > 1.0) {
            
            PPSSignaturePoint v = ViewPointToGL(l, self.bounds, StrokeColor);
            [self addTriangleStripPointsForPrevious:previousVertex next:v];
            
            previousVertex = v;            
            previousThickness = penThickness;
        }
        
        previousPoint = l;
        previousMidPoint = mid;

    } else if (p.state == UIGestureRecognizerStateEnded | p.state == UIGestureRecognizerStateCancelled) {
        
        PPSSignaturePoint v = ViewPointToGL(l, self.bounds, (GLKVector3){1, 1, 1});
        addVertex(&length, v);
        
        previousVertex = v;
        addVertex(&length, previousVertex);
    }
    
	[self setNeedsDisplay];
}


- (void)setStrokeColor:(UIColor *)strokeColor {
    _strokeColor = strokeColor;
    [self updateStrokeColor];
}


#pragma mark - Private

- (void)updateStrokeColor {

    self.effect.constantColor = GLKVector4Make(_colorR, _colorG, _colorB, _alpha);
}


- (void)setBackgroundColor:(UIColor *)backgroundColor {
    [super setBackgroundColor:backgroundColor];
    
    CGFloat red, green, blue, alpha, white;
    if ([backgroundColor getRed:&red green:&green blue:&blue alpha:&alpha]) {
        clearColor[0] = red;
        clearColor[1] = green;
        clearColor[2] = blue;
    } else if ([backgroundColor getWhite:&white alpha:&alpha]) {
        clearColor[0] = white;
        clearColor[1] = white;
        clearColor[2] = white;
    }
}

- (void)bindShaderAttributes {
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(PPSSignaturePoint), 0);
//    glEnableVertexAttribArray(GLKVertexAttribColor);
//    glVertexAttribPointer(GLKVertexAttribColor, 3, GL_FLOAT, GL_FALSE,  6 * sizeof(GLfloat), (char *)12);
}

- (void)setupGL
{
    [EAGLContext setCurrentContext:context];
    
    self.effect = [[GLKBaseEffect alloc] init];
    
    [self updateStrokeColor];

    
    glDisable(GL_DEPTH_TEST);
    
    // Signature Lines
    glGenVertexArraysOES(1, &vertexArray);
    glBindVertexArrayOES(vertexArray);
    
    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(SignatureVertexData), SignatureVertexData, GL_DYNAMIC_DRAW);
    [self bindShaderAttributes];
    
    
    // Signature Dots
    glGenVertexArraysOES(1, &dotsArray);
    glBindVertexArrayOES(dotsArray);
    
    glGenBuffers(1, &dotsBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, dotsBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(SignatureDotsData), SignatureDotsData, GL_DYNAMIC_DRAW);
    [self bindShaderAttributes];
    
    
    glBindVertexArrayOES(0);


    // Perspective
    GLKMatrix4 ortho = GLKMatrix4MakeOrtho(-1, 1, -1, 1, 0.1f, 2.0f);
    self.effect.transform.projectionMatrix = ortho;
    
    GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.0f);
    self.effect.transform.modelviewMatrix = modelViewMatrix;
    
    length = 0;
    penThickness = 0.003;
    previousPoint = CGPointMake(-100, -100);
}



- (void)addTriangleStripPointsForPrevious:(PPSSignaturePoint)previous next:(PPSSignaturePoint)next {
    float toTravel = penThickness / 2.0;
    
    for (int i = 0; i < 2; i++) {
        GLKVector3 p = perpendicular(previous, next);
        GLKVector3 p1 = next.vertex;
        GLKVector3 ref = GLKVector3Add(p1, p);
        
        float distance = GLKVector3Distance(p1, ref);
        float difX = p1.x - ref.x;
        float difY = p1.y - ref.y;
        float ratio = -1.0 * (toTravel / distance);
        
        difX = difX * ratio;
        difY = difY * ratio;
                
        PPSSignaturePoint stripPoint = {
            { p1.x + difX, p1.y + difY, 0.0 },
            StrokeColor
        };
        addVertex(&length, stripPoint);
        
        toTravel *= -1;
    }
}


- (void)tearDownGL
{
    [EAGLContext setCurrentContext:context];
    
    glDeleteVertexArraysOES(1, &vertexArray);
    glDeleteBuffers(1, &vertexBuffer);
    
    glDeleteVertexArraysOES(1, &dotsArray);
    glDeleteBuffers(1, &dotsBuffer);
    
    self.effect = nil;
}

@end