如何改变UIImage部分的颜色?

时间:2015-11-04 11:51:24

标签: ios objective-c bitmap uiimage cgbitmapcontextcreate

我有一张灰度图像,我在图像的某些部分应用它的原始颜色,我已经实现了它。现在我想改变我在图像中应用原始颜色的部分的颜色

我有这个: Original Image

我想转换成: Result Image

CGImageRef imageRef = [image CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);

NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;

NSUInteger bytesCount = height * width * bytesPerPixel;

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = (unsigned char *)calloc(bytesCount, sizeof(unsigned char));
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                             bitsPerComponent, bytesPerRow, colorSpace,
                                             kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);

unsigned char *outputData = (unsigned char *)calloc(bytesCount, sizeof(unsigned char));

NSUInteger byteIndex = 0;
for (NSUInteger i=0; i<bytesCount / bytesPerPixel; ++i) {
    CGFloat red = (CGFloat)rawData[byteIndex];
    CGFloat green = (CGFloat)rawData[byteIndex+1];
    CGFloat blue = (CGFloat)rawData[byteIndex+2];
    CGFloat alpha = (CGFloat)rawData[byteIndex+3];

    BOOL grayscale = red == green == blue;

    if (!grayscale) {
        // test for near values
        CGFloat diff = MAX(ABS(red-green), MAX(ABS(red-blue), ABS(green-blue)));

        static CGFloat allowedDifference = 100; // in range of 0-255

        if (diff > allowedDifference) {

//                CGFloat redTemp = 236;
//                red = green;
//                green = redTemp;
            red = 236.0;
            green = 17.0;
            blue = 17.0;

        }
    }

    outputData[byteIndex] = red;
    outputData[byteIndex+1] = green;
    outputData[byteIndex+2] = blue;
    outputData[byteIndex+3] = alpha;

    byteIndex += bytesPerPixel;
}

free(rawData);


CGDataProviderRef outputDataProvider = CGDataProviderCreateWithData(NULL,
                                                                    outputData,
                                                                    bytesCount,
                                                                    NULL);
free(outputData);

CGImageRef outputImageRef = CGImageCreate(width,
                                          height,
                                          bitsPerComponent,
                                          bytesPerPixel * 8,
                                          bytesPerRow,
                                          colorSpace,
                                          kCGBitmapByteOrderDefault,
                                          outputDataProvider,
                                          NULL,NO,
                                          kCGRenderingIntentDefault);


CGColorSpaceRelease(colorSpace);
CGDataProviderRelease(outputDataProvider);

UIImage *outputImage = [UIImage imageWithCGImage:outputImageRef];
CGImageRelease(outputImageRef);

我尝试了bitmapcontext和所有内容,但没有得到理想的结果。

有人有想法吗?

1 个答案:

答案 0 :(得分:1)

您可以尝试使用CGBitmapContextCreate从图像抓取像素数据来创建颜色空间,然后通过CGContextDrawImage将图像绘制到它。

其次,您将收到一个维度的字节数组。 像这样:[r1,g1,b1,a1,r2,g2,b2,a2,...]其中r,g,b,a - 颜色成分,1,2 - nu。像素。

在此之后,您可以迭代数组并比较每个像素的颜色分量。由于你应该跳过灰度像素,你需要比较rgb参数,理论上它们必须相等,但你也可以支持几个数字的一​​些小错误+ - 。

如果具体像素不是灰度,只需交换红色和绿色字节。

应该是要走的路。

更新了示例:

UIImage *image = [UIImage imageNamed:@"qfjsc.png"];

CGImageRef imageRef = [image CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);

NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;

NSUInteger bytesCount = height * width * bytesPerPixel;

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = (unsigned char *)calloc(bytesCount, sizeof(unsigned char));
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                             bitsPerComponent, bytesPerRow, colorSpace,
                                             kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);

unsigned char *outputData = (unsigned char *)calloc(bytesCount, sizeof(unsigned char));

NSUInteger byteIndex = 0;
for (NSUInteger i=0; i<bytesCount / bytesPerPixel; ++i) {
    CGFloat red = (CGFloat)rawData[byteIndex];
    CGFloat green = (CGFloat)rawData[byteIndex+1];
    CGFloat blue = (CGFloat)rawData[byteIndex+2];
    CGFloat alpha = (CGFloat)rawData[byteIndex+3];

    BOOL grayscale = red == green == blue;

    if (!grayscale) {
        // test for near values
        CGFloat diff = MAX(ABS(red-green), MAX(ABS(red-blue), ABS(green-blue)));

        static CGFloat allowedDifference = 50.0; // in range of 0-255

        if (diff > allowedDifference) {

            CGFloat redTemp = red;
            red = green;
            green = redTemp;

        }
    }

    outputData[byteIndex] = red;
    outputData[byteIndex+1] = green;
    outputData[byteIndex+2] = blue;
    outputData[byteIndex+3] = alpha;

    byteIndex += bytesPerPixel;
}

free(rawData);


CGDataProviderRef outputDataProvider = CGDataProviderCreateWithData(NULL,
                                                                    outputData,
                                                                    bytesCount,
                                                                    NULL);
free(outputData);

CGImageRef outputImageRef = CGImageCreate(width,
                                          height,
                                          bitsPerComponent,
                                          bytesPerPixel * 8,
                                          bytesPerRow,
                                          colorSpace,
                                          kCGBitmapByteOrderDefault,
                                          outputDataProvider,
                                          NULL,NO,
                                          kCGRenderingIntentDefault);


CGColorSpaceRelease(colorSpace);
CGDataProviderRelease(outputDataProvider);

UIImage *outputImage = [UIImage imageWithCGImage:outputImageRef];
CGImageRelease(outputImageRef);

请注意静态允许的差异变量。它允许您跳过几乎非灰度像素,但它们在RGB色彩空间中并且本质上几乎是灰度级。

以下是示例:

  1. 允许差异= 0 Allowed difference = 0
  2. 允许差异= 50 Allowed difference = 50