使用bitmapData修改镜像
使用bitmapData修改镜像
提问于 2021-03-14 00:29:50
所以我有一个方法，可以成功地获取像素的颜色。
//arrColT is an NSMutableArray<NSColor *>
NSInteger width = [bitIn pixelsWide];
NSInteger height = [bitIn pixelsHigh];
NSInteger rowBytes = [bitIn bytesPerRow];
unsigned char* pixels = [bitIn bitmapData];
int row, col;
//For every row,
for (row = 0; row < height; row++)
{
unsigned char* rowStart = (unsigned char*)(pixels + (row * rowBytes));
unsigned char* nextChannel = rowStart;
//For every pixel in a row,
for (col = 0; col < width; col++)
{
//Get its color.
unsigned char red, green, blue, alpha;
red = *nextChannel;
int intRed = (int)red;
nextChannel++;
green = *nextChannel;
int intGreen = (int)green;
nextChannel++;
blue = *nextChannel;
int intBlue = (int)blue;
nextChannel++;
alpha = *nextChannel;
int intAlpha = (int)alpha;
nextChannel++;
NSColor *colHas = [NSColor colorWithCalibratedRed:(float)intRed/255 green: (float)intGreen/255 blue: (float)intBlue/255 alpha:(float)intAlpha/255];
for (int i = 0; i<[arrColT count]; i++) {
//If the target color is equal to the current color, replace it with the parallel replace color...somehow.
if([colHas isEqualTo:arrColT[i]]){
}
}
}
}问题是，如何将颜色数据返回到bitmapData中？
带着希望，
radzo73
回答 2
Stack Overflow用户
发布于 2021-03-14 09:55:10
请参阅Technical Q&A QA1509，它基本上建议
- 创建像素缓冲区(通过创建预定义格式的
CGContextRef并根据需要绘制图像以在该像素缓冲区中创建字节； - 使用
CGBitmapContextCreateImage.
创建结果图像
例如。
- (UIImage *)convertImage:(UIImage *)image
{
// get image
CGImageRef imageRef = image.CGImage;
// prepare context
CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big; // bytes in RGBA order
NSInteger width = CGImageGetWidth(imageRef);
NSInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, 4 * width, colorspace, bitmapInfo);
// draw image to that context
CGRect rect = CGRectMake(0, 0, width, height);
CGContextDrawImage(context, rect, imageRef);
uint8_t *buffer = CGBitmapContextGetData(context);
// ... manipulate pixel buffer bytes here ...
// get image from buffer
CGImageRef outputImage = CGBitmapContextCreateImage(context);
UIImage *result = [UIImage imageWithCGImage:outputImage scale:image.scale orientation:image.imageOrientation];
// clean up
CGImageRelease(outputImage);
CGContextRelease(context);
CGColorSpaceRelease(colorspace);
return result;
}例如，下面是一个黑白转换例程：
/** Convert the image to B&W as a single (non-parallel) task.
*
* This assumes the pixel buffer is in RGBA, 8 bits per pixel format.
*
* @param buffer The pixel buffer.
* @param width The image width in pixels.
* @param height The image height in pixels.
*/
- (void)convertToBWSimpleInBuffer:(uint8_t *)buffer width:(NSInteger)width height:(NSInteger)height
{
for (NSInteger row = 0; row < height; row++) {
for (NSInteger col = 0; col < width; col++) {
NSUInteger offset = (col + row * width) * 4;
uint8_t *pixel = buffer + offset;
// get the channels
uint8_t red = pixel[0];
uint8_t green = pixel[1];
uint8_t blue = pixel[2];
uint8_t alpha = pixel[3];
// update the channels with result
uint8_t gray = 0.2126 * red + 0.7152 * green + 0.0722 * blue;
pixel[0] = gray;
pixel[1] = gray;
pixel[2] = gray;
pixel[3] = alpha;
}
}
}如果想要提高性能，可以并行使用dispatch_apply和stride遍历图像缓冲区：
/** Convert the image to B&W, using GCD to split the conversion into several concurrent GCD tasks.
*
* This assumes the pixel buffer is in RGBA, 8 bits per pixel format.
*
* @param buffer The pixel buffer.
* @param width The image width in pixels.
* @param height The image height in pixels.
* @param count How many GCD tasks should the conversion be split into.
*/
- (void)convertToBWConcurrentInBuffer:(uint8_t *)buffer width:(NSInteger)width height:(NSInteger)height count:(NSInteger)count
{
dispatch_queue_t queue = dispatch_queue_create("com.domain.app", DISPATCH_QUEUE_CONCURRENT);
NSInteger stride = height / count;
dispatch_apply(height / stride, queue, ^(size_t idx) {
size_t j = idx * stride;
size_t j_stop = MIN(j + stride, height);
for (NSInteger row = j; row < j_stop; row++) {
for (NSInteger col = 0; col < width; col++) {
NSUInteger offset = (col + row * width) * 4;
uint8_t *pixel = buffer + offset;
// get the channels
uint8_t red = pixel[0];
uint8_t green = pixel[1];
uint8_t blue = pixel[2];
uint8_t alpha = pixel[3];
// update the channels with result
uint8_t gray = 0.2126 * red + 0.7152 * green + 0.0722 * blue;
pixel[0] = gray;
pixel[1] = gray;
pixel[2] = gray;
pixel[3] = alpha;
}
}
});
}Stack Overflow用户
发布于 2021-03-14 10:02:04
这取决于bitIn是什么，但像这样的东西应该能起到作用。
首先，创建一个上下文。如果您要对数据进行大量更改并需要大量图片，您可以执行此操作一次，并保留上下文。
self.ctx = CGBitmapContextCreate (
[bitIn bitmapData],
[bitIn pixelsWide],
[bitIn pixelsHigh],
[bitIn bitsPerPixel],
[bitIn bytesPerRow],
[bitIn colorSpace],
[bitIn bitmapInfo] );在这里，我自由地使用了bitIn，希望它能提供所有缺失的部分。然后，即使对数据进行了进一步更改，也可以在以后将其组合在一起，使用如下代码
CGImageRef cgImg = CGBitmapContextCreateImage ( self.ctx );
UIImage * img = [UIImage imageWithCGImage:cgImg];
CGImageRelease ( cgImg );现在，您可以对数据进行更多更改，并执行相同的操作以获得新图像。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/66615908
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