公司最近要做一个拾色器,就是自己手动选择一张图片,获取手指点击的哪一个点的颜色,然后跳转其他页面,做颜色调试.
思考的问题:
1.刚接到这需求的时候,在网上搜了一下方法,获取点击点的颜色方法很多,但是都有一个弊端,就是一定要求,UIImageView的frame一定要跟图片一样,才能准确获取点得色彩.
2.因为还需要对图片做缩放的功能,考虑到可以把图片放到scrollView和在图片上添加手势两种方法(鉴于没有经验,只好都尝试一遍,发现scrollView是完美的)
3.获取手指点击的坐标,一开始通过添加手势来缩放,可以直接调用系统TouchBegin方法获取,但是将imageView放在scrollView中,次方法获取不到坐标点,只能对imageView添加一个单点击手势.
实现思路:
1.获取需要展示的图片,并且拿到款和高,添加一个bgImageView,frame设置为图片大小,直接添加到当前控制器View上.
2.添加一个scrollView到控制器View上,frame设置为view.bounds.
3.获取需要展示的图片,并且拿到图片的宽和高.然后除以当前屏幕宽和高,获取一个比例scale.添加一个imageView到scrollView上,frame是经过比例缩放的.
4.添加一个单击手势给imageView,实现对应的方法通过手势方法获取点:CGPoint point = [sender locationInView:_imageView].
5.在获取色调的方法中,传进去的image是bgImageView的image属性,坐标点是乘以刚刚第二步计算的出来的scale,这样,点击屏幕的点就可以准确获取到图片对应点得颜色.
贴出获取色彩的代码:
- (UIColor*)getPixelColorAtLocation:(CGPoint)point
{ UIColor* color = [UIColor whiteColor];
[self.colorArr removeAllObjects];
if (point.x < self.imageView.frame.size.width && point.x > 0 && point.y < self.imageView.frame.size.height && point.y > 0) { UIImageView *colorImageView=self.backgroundImageV; CGImageRef inImage = colorImageView.image.CGImage;
// Create off screen bitmap context to draw the image into. Format ARGB is 4 bytes for each pixel: Alpa, Red, Green, Blue
CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];
if (cgctx == NULL)
{
return nil;
}
size_t w = CGImageGetWidth(inImage);
size_t h = CGImageGetHeight(inImage);
CGRect rect = {{0,0},{w,h}};
// Draw the image to the bitmap context. Once we draw, the memory
// allocated for the context for rendering will then contain the
// raw image data in the specified color space.
CGContextDrawImage(cgctx, rect, inImage);
// Now we can get a pointer to the image data associated with the bitmap
// context.
unsignedchar* data = CGBitmapContextGetData (cgctx);
if (data != NULL)
{//offset locates the pixel in the data from x,y.
//4 for 4 bytes of data per pixel, w is width of one row of data.
@try
{
int offset = 4*((w*round(point.y * self.scale))+round(point.x * self.scale));
//NSLog(@"offset: %d", offset);
int alpha = data[offset];
int red = data[offset+1];
int green = data[offset+2];
int blue = data[offset+3]; // NSLog(@"offset: %i colors: RGB A %i %i %i %i",offset,red,green,blue,alpha);
NSLog(@"%d%d%d",red,green,blue);
[self.colorArr addObject:@(alpha / 255.0f)];
[self.colorArr addObject:@(red)];
[self.colorArr addObject:@(green)];
[self.colorArr addObject:@(blue)];
color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:(blue/255.0f) alpha:(alpha/255.0f)]; }
@catch (NSException * e)
{
NSLog(@"%@",[e reason]);
}
@finally
{
}
}
// When finished, release the context
CGContextRelease(cgctx);
// Free image data memory for the context
if (data)
{
free(data);
}
}
self.pickView.backgroundColor = color;
return color;
}
- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {
CGContextRef context =NULL;
CGColorSpaceRef colorSpace;
voidvoid * bitmapData;
int bitmapByteCount;
int bitmapBytesPerRow;
// Get image width, height. We'll use the entire image.
size_t pixelsWide = CGImageGetWidth(inImage);
size_t pixelsHigh = CGImageGetHeight(inImage);
// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow = (int)(pixelsWide * 4);
bitmapByteCount =(int)(bitmapBytesPerRow * pixelsHigh);
// Use the generic RGB color space.
colorSpace = CGColorSpaceCreateDeviceRGB();
if (colorSpace == NULL)
{
fprintf(stderr,"Error allocating color space\n");
return NULL;
}
// Allocate memory for image data. This is the destination in memory
// where any drawing to the bitmap context will be rendered.
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
fprintf (stderr,"Memory not allocated!");
CGColorSpaceRelease( colorSpace );
return NULL;
}
// Create the bitmap context. We want pre-multiplied ARGB, 8-bits
// per component. Regardless of what the source image format is
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.
context = CGBitmapContextCreate (bitmapData,
pixelsWide,
pixelsHigh,
8, // bits per component
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedFirst);
if (context == NULL)
{
free (bitmapData);
fprintf (stderr,"Context not created!");
}
// Make sure and release colorspace before returning
CGColorSpaceRelease( colorSpace );
return context;
}
到此,此功能需求完美实现,需要源码的小伙伴,可以留言交流~
