最近在一个项目中，需要实现这么一个效果：显示一张地图，通过点击不同位置，来切换点击处的行政区域，效果图如下：
map.gif
在此记录一下实现思路：
- 1.首先要有一组需要展示的不同地区的图片，我的图片如下：
maps.png
这里要注意，要留意map_whs这张图片的尺寸，因为代码中需要使用到这个尺寸。
- 2.然后，你需要知道每个地区所对应的地图颜色，我的地图对于颜色如下：
colors.png
我自己写了个JSON文件，用来保存对应的颜色、名称以及图片名称。
- 3.在代码中，创建一个UIImageView，这个UIImageView的宽高比例要与刚才提到的map_whs图片的宽高比例一致，同时，计算出UIImageView的宽(或者高)与map_whs的宽(或者高)德比例，然后为UIImageView添加点击事件：
self.mapImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, self.nameLabel.plt_y + self.nameLabel.plt_height, self.view.plt_width, self.view.plt_width / (kMapImageWidth / kMapImageHeight))];
UITapGestureRecognizer *mapImageViewTGR = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(mapImageViewTGRAction:)];
[self.mapImageView addGestureRecognizer:mapImageViewTGR];
self.mapImageView.userInteractionEnabled = YES;
[self.view addSubview:self.mapImageView];
- 4.处理点击事件，获取到的点击位置，要根据上一步计算的比例来对应到map_whs这张图片的点上：
- (void)mapImageViewTGRAction:(UITapGestureRecognizer *)tgr
{
//触点位置
CGPoint touchLocation = [tgr locationInView:self.mapImageView];
if (touchLocation.x > 0 && touchLocation.x <= self.mapImageView.plt_width && touchLocation.y > 0 && touchLocation.y <= self.mapImageView.plt_height) {
//触点颜色
UIColor *positionColor=[self getColor:touchLocation];
for (NSDictionary *dic in self.txtArr) {
UIColor *color = PltColorWithHEX(dic[kMapTxtColor]);
if (CGColorEqualToColor(color.CGColor, positionColor.CGColor)) {
[self setUpImage:dic];
break;
}
}
}
}
#pragma mark - 获取点击颜色
- (UIColor *)getColor:(CGPoint)point
{
UIColor* color = [UIColor whiteColor];
if (point.x > 0 && point.y > 0) {
CGFloat ratio = kMapImageWidth / self.mapImageView.plt_width;
CGPoint realPoint = CGPointMake(point.x * ratio, point.y * ratio);
CGImageRef inImage = [UIImage imageNamed:@"map_whs"].CGImage;
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.
unsigned char* 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(realPoint.y))+round(realPoint.x));
//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);
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);
}
}
return color;
}
- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage
{
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
void * 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;
}
