使用 CYMK 值绘制图像
Draw Image using CYMK values
我想在不使用自动转换工具或库的情况下将缓冲图像从 RGBA 格式转换为 CYMK 格式,因此我尝试从使用 BufferedImage.getRGB()
获得的单个像素中提取 RGBA 值,这就是我所做的到目前为止已完成:
BufferedImage img = new BufferedImage("image path")
int R,G,B,pixel,A;
float Rc,Gc,Bc,K,C,M,Y;
int height = img.getHeight();
int width = img.getWidth();
for(int y = 0 ; y < height ; y++){
for(int x = 0 ; x < width ; x++){
pixel = img.getRGB(x, y);
//I shifted the int bytes to get RGBA values
A = (pixel>>24)&0xff;
R = (pixel>>16)&0xff;
G = (pixel>>8)&0xff;
B = (pixel)&0xff;
Rc = (float) ((float)R/255.0);
Gc = (float) ((float)G/255.0);
Bc = (float) ((float)B/255.0);
// Equations i found on the internet to get CYMK values
K = 1 - Math.max(Bc, Math.max(Rc, Gc));
C = (1- Rc - K)/(1-K);
Y = (1- Bc - K)/(1-K);
M = (1- Gc - K)/(1-K);
}
}
在我提取它之后,我想使用这些值绘制或构建图像,你能告诉我一种方法或方法吗,因为我认为BufferedImage.setRGB()
不会工作,而且当我打印 C,Y,M
的值时,其中一些值具有 NaN
值,有人可以告诉我这意味着什么以及如何处理它吗?
虽然可以,但在没有正确颜色配置文件的情况下将 RGB 转换为 CMYK 不会产生最佳效果。为了获得更好的性能和更高的颜色保真度,我真的建议使用 ICC 颜色配置文件(参见 ICC_Profile
和 ICC_ColorSpace
类)和 ColorConvertOp
。 :-)
无论如何,下面是如何使用您自己的转换来完成此操作。重要的部分是创建 CMYK 颜色 space,以及使用该颜色 space 的 ColorModel
和 BufferedImage
(您也可以从如上所述的 ICC 配置文件,但颜色可能看起来更差,因为它使用与您不同的计算)。
public static void main(String[] args) throws IOException {
BufferedImage img = ImageIO.read(new File(args[0]));
int height = img.getHeight();
int width = img.getWidth();
// Create a color model and image in CMYK color space (see custom class below)
ComponentColorModel cmykModel = new ComponentColorModel(CMYKColorSpace.INSTANCE, false, false, Transparency.TRANSLUCENT, DataBuffer.TYPE_BYTE);
BufferedImage cmykImg = new BufferedImage(cmykModel, cmykModel.createCompatibleWritableRaster(width, height), cmykModel.isAlphaPremultiplied(), null);
WritableRaster cmykRaster = cmykImg.getRaster();
int R,G,B,pixel;
float Rc,Gc,Bc,K,C,M,Y;
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
pixel = img.getRGB(x, y);
// Now, as cmykImg already is in CMYK color space, you could actually just invoke
//cmykImg.setRGB(x, y, pixel);
// and the method would perform automatic conversion to the dest color space (CMYK)
// But, here you go... (I just cleaned up your code a little bit):
R = (pixel >> 16) & 0xff;
G = (pixel >> 8) & 0xff;
B = (pixel) & 0xff;
Rc = R / 255f;
Gc = G / 255f;
Bc = B / 255f;
// Equations I found on the internet to get CMYK values
K = 1 - Math.max(Bc, Math.max(Rc, Gc));
if (K == 1f) {
// All black (this is where you would get NaN values I think)
C = M = Y = 0;
}
else {
C = (1- Rc - K)/(1-K);
M = (1- Gc - K)/(1-K);
Y = (1- Bc - K)/(1-K);
}
// ...and store the CMYK values (as bytes in 0..255 range) in the raster
cmykRaster.setDataElements(x, y, new byte[] {(byte) (C * 255), (byte) (M * 255), (byte) (Y * 255), (byte) (K * 255)});
}
}
// You should now have a CMYK buffered image
System.out.println("cmykImg: " + cmykImg);
}
// A simple and not very accurate CMYK color space
// Full source at https://github.com/haraldk/TwelveMonkeys/blob/master/imageio/imageio-core/src/main/java/com/twelvemonkeys/imageio/color/CMYKColorSpace.java
final static class CMYKColorSpace extends ColorSpace {
static final ColorSpace INSTANCE = new CMYKColorSpace();
final ColorSpace sRGB = getInstance(CS_sRGB);
private CMYKColorSpace() {
super(ColorSpace.TYPE_CMYK, 4);
}
public static ColorSpace getInstance() {
return INSTANCE;
}
public float[] toRGB(float[] colorvalue) {
return new float[]{
(1 - colorvalue[0]) * (1 - colorvalue[3]),
(1 - colorvalue[1]) * (1 - colorvalue[3]),
(1 - colorvalue[2]) * (1 - colorvalue[3])
};
}
public float[] fromRGB(float[] rgbvalue) {
// NOTE: This is essentially the same equation you use, except
// this is slightly optimized, and values are already in range [0..1]
// Compute CMY
float c = 1 - rgbvalue[0];
float m = 1 - rgbvalue[1];
float y = 1 - rgbvalue[2];
// Find K
float k = Math.min(c, Math.min(m, y));
// Convert to CMYK values
return new float[]{(c - k), (m - k), (y - k), k};
}
public float[] toCIEXYZ(float[] colorvalue) {
return sRGB.toCIEXYZ(toRGB(colorvalue));
}
public float[] fromCIEXYZ(float[] colorvalue) {
return sRGB.fromCIEXYZ(fromRGB(colorvalue));
}
}
PS:你的问题说的是RGBA和CMYK,但是你的代码只是忽略了alpha值,所以我也照做了。如果您真的想要,您可以保持 alpha 值不变并拥有 CMYK+A 图像,以允许 CMYK 颜色 space 中的 alpha 合成。我会把它留作练习。 ;-)
我想在不使用自动转换工具或库的情况下将缓冲图像从 RGBA 格式转换为 CYMK 格式,因此我尝试从使用 BufferedImage.getRGB()
获得的单个像素中提取 RGBA 值,这就是我所做的到目前为止已完成:
BufferedImage img = new BufferedImage("image path")
int R,G,B,pixel,A;
float Rc,Gc,Bc,K,C,M,Y;
int height = img.getHeight();
int width = img.getWidth();
for(int y = 0 ; y < height ; y++){
for(int x = 0 ; x < width ; x++){
pixel = img.getRGB(x, y);
//I shifted the int bytes to get RGBA values
A = (pixel>>24)&0xff;
R = (pixel>>16)&0xff;
G = (pixel>>8)&0xff;
B = (pixel)&0xff;
Rc = (float) ((float)R/255.0);
Gc = (float) ((float)G/255.0);
Bc = (float) ((float)B/255.0);
// Equations i found on the internet to get CYMK values
K = 1 - Math.max(Bc, Math.max(Rc, Gc));
C = (1- Rc - K)/(1-K);
Y = (1- Bc - K)/(1-K);
M = (1- Gc - K)/(1-K);
}
}
在我提取它之后,我想使用这些值绘制或构建图像,你能告诉我一种方法或方法吗,因为我认为BufferedImage.setRGB()
不会工作,而且当我打印 C,Y,M
的值时,其中一些值具有 NaN
值,有人可以告诉我这意味着什么以及如何处理它吗?
虽然可以,但在没有正确颜色配置文件的情况下将 RGB 转换为 CMYK 不会产生最佳效果。为了获得更好的性能和更高的颜色保真度,我真的建议使用 ICC 颜色配置文件(参见 ICC_Profile
和 ICC_ColorSpace
类)和 ColorConvertOp
。 :-)
无论如何,下面是如何使用您自己的转换来完成此操作。重要的部分是创建 CMYK 颜色 space,以及使用该颜色 space 的 ColorModel
和 BufferedImage
(您也可以从如上所述的 ICC 配置文件,但颜色可能看起来更差,因为它使用与您不同的计算)。
public static void main(String[] args) throws IOException {
BufferedImage img = ImageIO.read(new File(args[0]));
int height = img.getHeight();
int width = img.getWidth();
// Create a color model and image in CMYK color space (see custom class below)
ComponentColorModel cmykModel = new ComponentColorModel(CMYKColorSpace.INSTANCE, false, false, Transparency.TRANSLUCENT, DataBuffer.TYPE_BYTE);
BufferedImage cmykImg = new BufferedImage(cmykModel, cmykModel.createCompatibleWritableRaster(width, height), cmykModel.isAlphaPremultiplied(), null);
WritableRaster cmykRaster = cmykImg.getRaster();
int R,G,B,pixel;
float Rc,Gc,Bc,K,C,M,Y;
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
pixel = img.getRGB(x, y);
// Now, as cmykImg already is in CMYK color space, you could actually just invoke
//cmykImg.setRGB(x, y, pixel);
// and the method would perform automatic conversion to the dest color space (CMYK)
// But, here you go... (I just cleaned up your code a little bit):
R = (pixel >> 16) & 0xff;
G = (pixel >> 8) & 0xff;
B = (pixel) & 0xff;
Rc = R / 255f;
Gc = G / 255f;
Bc = B / 255f;
// Equations I found on the internet to get CMYK values
K = 1 - Math.max(Bc, Math.max(Rc, Gc));
if (K == 1f) {
// All black (this is where you would get NaN values I think)
C = M = Y = 0;
}
else {
C = (1- Rc - K)/(1-K);
M = (1- Gc - K)/(1-K);
Y = (1- Bc - K)/(1-K);
}
// ...and store the CMYK values (as bytes in 0..255 range) in the raster
cmykRaster.setDataElements(x, y, new byte[] {(byte) (C * 255), (byte) (M * 255), (byte) (Y * 255), (byte) (K * 255)});
}
}
// You should now have a CMYK buffered image
System.out.println("cmykImg: " + cmykImg);
}
// A simple and not very accurate CMYK color space
// Full source at https://github.com/haraldk/TwelveMonkeys/blob/master/imageio/imageio-core/src/main/java/com/twelvemonkeys/imageio/color/CMYKColorSpace.java
final static class CMYKColorSpace extends ColorSpace {
static final ColorSpace INSTANCE = new CMYKColorSpace();
final ColorSpace sRGB = getInstance(CS_sRGB);
private CMYKColorSpace() {
super(ColorSpace.TYPE_CMYK, 4);
}
public static ColorSpace getInstance() {
return INSTANCE;
}
public float[] toRGB(float[] colorvalue) {
return new float[]{
(1 - colorvalue[0]) * (1 - colorvalue[3]),
(1 - colorvalue[1]) * (1 - colorvalue[3]),
(1 - colorvalue[2]) * (1 - colorvalue[3])
};
}
public float[] fromRGB(float[] rgbvalue) {
// NOTE: This is essentially the same equation you use, except
// this is slightly optimized, and values are already in range [0..1]
// Compute CMY
float c = 1 - rgbvalue[0];
float m = 1 - rgbvalue[1];
float y = 1 - rgbvalue[2];
// Find K
float k = Math.min(c, Math.min(m, y));
// Convert to CMYK values
return new float[]{(c - k), (m - k), (y - k), k};
}
public float[] toCIEXYZ(float[] colorvalue) {
return sRGB.toCIEXYZ(toRGB(colorvalue));
}
public float[] fromCIEXYZ(float[] colorvalue) {
return sRGB.fromCIEXYZ(fromRGB(colorvalue));
}
}
PS:你的问题说的是RGBA和CMYK,但是你的代码只是忽略了alpha值,所以我也照做了。如果您真的想要,您可以保持 alpha 值不变并拥有 CMYK+A 图像,以允许 CMYK 颜色 space 中的 alpha 合成。我会把它留作练习。 ;-)