explain it in easy way ---**Color Models**
**RGB to YCbCr Conversion Formulas**
YCbCr is a color space that separates luminance (brightness) from chrominance (color information), widely used in video compression (e.g., JPEG, MPEG). Below are the standard conversion formulas for 8-bit RGB (0-255) to YCbCr (Y: 0-255, Cb/Cr: 16-240).
**Step-by-Step Conversion**
**1. Normalize RGB Values**
First, scale the 8-bit RGB values to the range **[0, 1]**:
R' = R / 255, G' = G / 255, B' = B / 255
**2. Compute Luminance (Y)**
Y = 16 + 65.481 * R' + 128.553 * G' + 24.966 * B'
**3. Compute Chrominance (Cb and Cr)**
Cb = 128 - 37.797 * R' - 74.203 * G' + 112.0 * B'
Cr = 128 + 112.0 * R' - 93.786 * G' - 18.214 * B'
**4. Clamp Values to Valid Ranges**
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Let's explore color models! RGB mixes red, green, and blue light to create all the colors you see on your computer screen. YCbCr is different - it separates the brightness from the color information. This separation is very useful for video compression because it helps make video files much smaller while keeping good quality.
The first step in converting RGB to YCbCr is to normalize the RGB values. Your computer typically uses numbers from 0 to 255 for red, green, and blue. We need to change these to be between 0 and 1 by dividing each value by 255. For example, if we have RGB values of 255, 128, and 64, we divide each by 255 to get 1.0, 0.5, and 0.25. This normalization step prepares our values for the mathematical formulas we'll use next.
The second step is to calculate the brightness, also called luminance or Y value. We use a special mathematical formula that weighs the green component the most, then red, then blue. This is because our eyes are most sensitive to green light. The formula starts with 16 and adds weighted amounts of our normalized red, green, and blue values. Using our example values of 1.0, 0.5, and 0.25, we get a brightness value of 152, which represents a medium-bright color.
The third step calculates the color information using two values: Cb and Cr. Cb tells us how much blue versus yellow is in the color, while Cr tells us how much red versus green is present. Both formulas start with 128, which represents neutral color with no bias toward blue-yellow or red-green. Using our example values, we get Cb equals 81, indicating some yellow bias, and Cr equals 189, indicating a red bias. These values typically range from 16 to 240 in video standards.
We have successfully converted RGB to YCbCr! First, we normalized RGB values from the 0 to 255 range down to 0 to 1. Then we used the Y formula to calculate brightness using weighted RGB values, with green getting the most weight. Next, we calculated Cb and Cr to separate the blue-yellow and red-green color information. This YCbCr format is perfect for video compression because it separates brightness from color. Finally, we clamp the values to their valid ranges to ensure compatibility with video standards.