HSB Stack Conversion
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Good Morning … hope everyone is doing well today … I have a Nikon raw image (*.NEF) that I can convert to 16 bit TIFF using the Nikon software … from the 16 bit Tiff I can ultimately generate a 32 bit floating point LAB stack quite nicely with image/type …. but when I try to convert it to HSB stack or RGB stack it returns 8 bit images …. is there a way to generate 32 bit HSB stack? I'd like to examine the hue slice in detail but with an 8 bit stack it appears to be limited to only 255 hue angles … meaning the returned value for hue slice is not even close …. this may be a question for Wayne? … Please advise and thank you in advance …. have a blessed day … Lee
William L. Berndt, Ph.D. 7133 Penner Lane. Apt. #40Fort Myers, FL 33907@Dr_Lee_Berndt239.246.0396 -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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> On Jul 11, 2020, at 8:39 AM, Lee Berndt <[hidden email]> wrote:
> > Good Morning … hope everyone is doing well today … I have a Nikon raw image (*.NEF) that I can convert to 16 bit TIFF using the Nikon software … from the 16 bit Tiff I can ultimately generate a 32 bit floating point LAB stack quite nicely with image/type …. but when I try to convert it to HSB stack or RGB stack it returns 8 bit images …. is there a way to generate 32 bit HSB stack? I'd like to examine the hue slice in detail but with an 8 bit stack it appears to be limited to only 255 hue angles … meaning the returned value for hue slice is not even close …. this may be a question for Wayne? … Please advise and thank you in advance …. have a blessed day … Lee The latest ImageJ daily build (1.53d18) adds adds an Image>Type>HSB (32-bit) command. -wayne -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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Hello Wayne … thank you for responding …. and the 32-bit version of HSB stack is much appreciated … but when I look at the same image the Lab = 53.4, -15.9, 14.3 and its RGB equivalent is 109.4, 136.5, 104.5 … but the 32 bit version of HSB stack gives me hue = 0.301, satur. = 0.289, and brightness = 0.538 …. brightness is spot on but hue and saturation appear to be off (?) ….. the equivalent hue angle should be about 109° and saturation is 24% …. arctan(b/a) is about 2.4 …. how is the reported hue angle in 32 bit HSB stack being calculated or reported? please advise and thank you very much …. have a blessed day …. Lee
William L. Berndt, Ph.D. 7133 Penner Lane. Apt. #40Fort Myers, FL 33907@Dr_Lee_Berndt239.246.0396 -----Original Message----- From: Wayne Rasband <[hidden email]> To: [hidden email] Sent: Sat, Jul 11, 2020 11:32 am Subject: Re: HSB Stack Conversion > On Jul 11, 2020, at 8:39 AM, Lee Berndt <[hidden email]> wrote: > > Good Morning … hope everyone is doing well today … I have a Nikon raw image (*.NEF) that I can convert to 16 bit TIFF using the Nikon software … from the 16 bit Tiff I can ultimately generate a 32 bit floating point LAB stack quite nicely with image/type …. but when I try to convert it to HSB stack or RGB stack it returns 8 bit images …. is there a way to generate 32 bit HSB stack? I'd like to examine the hue slice in detail but with an 8 bit stack it appears to be limited to only 255 hue angles … meaning the returned value for hue slice is not even close …. this may be a question for Wayne? … Please advise and thank you in advance …. have a blessed day … Lee The latest ImageJ daily build (1.53d18) adds adds an Image>Type>HSB (32-bit) command. -wayne -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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On Saturday, 11 July 2020 18:48:05 BST Lee Berndt wrote:
> Hello Wayne … thank you for responding …. and the 32-bit version of HSB > stack is much appreciated … but when I look at the same image the Lab = > 53.4, -15.9, 14.3 and its RGB equivalent is 109.4, 136.5, 104.5 … but the > 32 bit version of HSB stack gives me hue = 0.301, satur. = 0.289, and > brightness = 0.538 … Just did a test with a full colour 24bit image and HSB channels are all scaled to the range 0..1 which seems very convenient. Cheers Gabriel -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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Hello Gabriel …. thank you for responding …. it makes sense now and I appreciate the work it took to produce this algorithm …. but if I might ask … the saturation component seems to be off a little bit …. LAB values of 57.9, -18.2, and 15.1 from a raw image (RGB = 116, 147,112) result in a saturation value of 24% but the 32-bit HSB stack reports saturatioin as 29% …. I checked these calculations with my own and using a commercial software package (independent calculations) …. any thoughts? How is the saturation component being calculated? Please advise and thank you in advance …. have a blessed day …. Lee
William L. Berndt, Ph.D. 7133 Penner Lane. Apt. #40Fort Myers, FL 33907@Dr_Lee_Berndt239.246.0396 -----Original Message----- From: Gabriel Landini <[hidden email]> To: [hidden email] Sent: Sat, Jul 11, 2020 2:40 pm Subject: Re: HSB Stack Conversion On Saturday, 11 July 2020 18:48:05 BST Lee Berndt wrote: > Hello Wayne … thank you for responding …. and the 32-bit version of HSB > stack is much appreciated … but when I look at the same image the Lab = > 53.4, -15.9, 14.3 and its RGB equivalent is 109.4, 136.5, 104.5 … but the > 32 bit version of HSB stack gives me hue = 0.301, satur. = 0.289, and > brightness = 0.538 … Just did a test with a full colour 24bit image and HSB channels are all scaled to the range 0..1 which seems very convenient. Cheers Gabriel -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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> On Jul 13, 2020, at 8:51 AM, Lee Berndt <[hidden email]> wrote:
> > Hello Gabriel …. thank you for responding …. it makes sense now and I appreciate the work it took to produce this algorithm …. but if I might ask … the saturation component seems to be off a little bit …. LAB values of 57.9, -18.2, and 15.1 from a raw image (RGB = 116, 147,112) result in a saturation value of 24% but the 32-bit HSB stack reports saturatioin as 29% …. I checked these calculations with my own and using a commercial software package (independent calculations) …. any thoughts? How is the saturation component being calculated? Please advise and thank you in advance …. have a blessed day …. Lee ImageJ uses Java's Color.RGBtoHSB() method to convert from RGB to HSB. The source code for this method is below. -wayne /** * Converts the components of a color, as specified by the default RGB * model, to an equivalent set of values for hue, saturation, and * brightness that are the three components of the HSB model. * <p> * If the <code>hsbvals</code> argument is <code>null</code>, then a * new array is allocated to return the result. Otherwise, the method * returns the array <code>hsbvals</code>, with the values put into * that array. * @param r the red component of the color * @param g the green component of the color * @param b the blue component of the color * @param hsbvals the array used to return the * three HSB values, or <code>null</code> * @return an array of three elements containing the hue, saturation, * and brightness (in that order), of the color with * the indicated red, green, and blue components. * @see java.awt.Color#getRGB() * @see java.awt.Color#Color(int) * @see java.awt.image.ColorModel#getRGBdefault() * @since JDK1.0 */ public static float[] RGBtoHSB(int r, int g, int b, float[] hsbvals) { float hue, saturation, brightness; if (hsbvals == null) { hsbvals = new float[3]; } int cmax = (r > g) ? r : g; if (b > cmax) cmax = b; int cmin = (r < g) ? r : g; if (b < cmin) cmin = b; brightness = ((float) cmax) / 255.0f; if (cmax != 0) saturation = ((float) (cmax - cmin)) / ((float) cmax); else saturation = 0; if (saturation == 0) hue = 0; else { float redc = ((float) (cmax - r)) / ((float) (cmax - cmin)); float greenc = ((float) (cmax - g)) / ((float) (cmax - cmin)); float bluec = ((float) (cmax - b)) / ((float) (cmax - cmin)); if (r == cmax) hue = bluec - greenc; else if (g == cmax) hue = 2.0f + redc - bluec; else hue = 4.0f + greenc - redc; hue = hue / 6.0f; if (hue < 0) hue = hue + 1.0f; } hsbvals[0] = hue; hsbvals[1] = saturation; hsbvals[2] = brightness; return hsbvals; } > > William L. Berndt, Ph.D. 7133 Penner Lane. Apt. #40Fort Myers, FL 33907@Dr_Lee_Berndt239.246.0396 > > -----Original Message----- > From: Gabriel Landini <[hidden email]> > To: [hidden email] > Sent: Sat, Jul 11, 2020 2:40 pm > Subject: Re: HSB Stack Conversion > > On Saturday, 11 July 2020 18:48:05 BST Lee Berndt wrote: >> Hello Wayne … thank you for responding …. and the 32-bit version of HSB >> stack is much appreciated … but when I look at the same image the Lab = >> 53.4, -15.9, 14.3 and its RGB equivalent is 109.4, 136.5, 104.5 … but the >> 32 bit version of HSB stack gives me hue = 0.301, satur. = 0.289, and >> brightness = 0.538 … > > Just did a test with a full colour 24bit image and HSB channels are all scaled > to the range 0..1 which seems very convenient. > > Cheers > > Gabriel -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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Hi everyone,
just for further clarification: For the RGB to HSB conversion, Java does not use an arctangent function but a kind of linear interpolation between the primary colors. It's the essentially same for the reverse transformation (HSB to RGB). You can find both methods in the wikipedia article: https://en.wikipedia.org/wiki/HSL_and_HSV#Hue_and_chroma For the primary colors RGB and the exact midpoints between them (yellow, magenta, cyan), the values are the same between these methods. For other values, there is a difference between the (arc)tangent and the java method. According Wikipedia, the maximum difference between the (arc)tangent and the Java method is 1.12°. So you should expect differences up to this magnitude when comparing different ways of converting RGB to HSB. Michael ________________________________________________________________ On 13.07.20 16:05, Wayne Rasband wrote: >> On Jul 13, 2020, at 8:51 AM, Lee Berndt <[hidden email]> wrote: >> >> Hello Gabriel …. thank you for responding …. it makes sense now and I appreciate the work it took to produce this algorithm …. but if I might ask … the saturation component seems to be off a little bit …. LAB values of 57.9, -18.2, and 15.1 from a raw image (RGB = 116, 147,112) result in a saturation value of 24% but the 32-bit HSB stack reports saturatioin as 29% …. I checked these calculations with my own and using a commercial software package (independent calculations) …. any thoughts? How is the saturation component being calculated? Please advise and thank you in advance …. have a blessed day …. Lee > > ImageJ uses Java's Color.RGBtoHSB() method to convert from RGB to HSB. The source code for this method is below. > > -wayne > > /** > * Converts the components of a color, as specified by the default RGB > * model, to an equivalent set of values for hue, saturation, and > * brightness that are the three components of the HSB model. > * <p> > * If the <code>hsbvals</code> argument is <code>null</code>, then a > * new array is allocated to return the result. Otherwise, the method > * returns the array <code>hsbvals</code>, with the values put into > * that array. > * @param r the red component of the color > * @param g the green component of the color > * @param b the blue component of the color > * @param hsbvals the array used to return the > * three HSB values, or <code>null</code> > * @return an array of three elements containing the hue, saturation, > * and brightness (in that order), of the color with > * the indicated red, green, and blue components. > * @see java.awt.Color#getRGB() > * @see java.awt.Color#Color(int) > * @see java.awt.image.ColorModel#getRGBdefault() > * @since JDK1.0 > */ > public static float[] RGBtoHSB(int r, int g, int b, float[] hsbvals) { > float hue, saturation, brightness; > if (hsbvals == null) { > hsbvals = new float[3]; > } > int cmax = (r > g) ? r : g; > if (b > cmax) cmax = b; > int cmin = (r < g) ? r : g; > if (b < cmin) cmin = b; > > brightness = ((float) cmax) / 255.0f; > if (cmax != 0) > saturation = ((float) (cmax - cmin)) / ((float) cmax); > else > saturation = 0; > if (saturation == 0) > hue = 0; > else { > float redc = ((float) (cmax - r)) / ((float) (cmax - cmin)); > float greenc = ((float) (cmax - g)) / ((float) (cmax - cmin)); > float bluec = ((float) (cmax - b)) / ((float) (cmax - cmin)); > if (r == cmax) > hue = bluec - greenc; > else if (g == cmax) > hue = 2.0f + redc - bluec; > else > hue = 4.0f + greenc - redc; > hue = hue / 6.0f; > if (hue < 0) > hue = hue + 1.0f; > } > hsbvals[0] = hue; > hsbvals[1] = saturation; > hsbvals[2] = brightness; > return hsbvals; > } > > >> >> William L. Berndt, Ph.D. 7133 Penner Lane. Apt. #40Fort Myers, FL 33907@Dr_Lee_Berndt239.246.0396 >> >> -----Original Message----- >> From: Gabriel Landini <[hidden email]> >> To: [hidden email] >> Sent: Sat, Jul 11, 2020 2:40 pm >> Subject: Re: HSB Stack Conversion >> >> On Saturday, 11 July 2020 18:48:05 BST Lee Berndt wrote: >>> Hello Wayne … thank you for responding …. and the 32-bit version of HSB >>> stack is much appreciated … but when I look at the same image the Lab = >>> 53.4, -15.9, 14.3 and its RGB equivalent is 109.4, 136.5, 104.5 … but the >>> 32 bit version of HSB stack gives me hue = 0.301, satur. = 0.289, and >>> brightness = 0.538 … >> >> Just did a test with a full colour 24bit image and HSB channels are all scaled >> to the range 0..1 which seems very convenient. >> >> Cheers >> >> Gabriel > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html > -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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