使用Photoshop计算图像像素平均暗度及对比苹果切片褐变程度的技术咨询

Hey there, totally get being stuck in that Photoshop rabbit hole—combining food science with image editing can feel super overwhelming when you’re not familiar with the tools, but let’s break this down in simple, actionable steps!

First, let’s clear up your grayscale question:

• Converting to grayscale does work for measuring "darkness" related to browning. Photoshop’s default grayscale conversion calculates brightness based on how the human eye perceives color (we’re most sensitive to green, so green contributes more to the final gray value). Since apple browning turns light flesh to darker brown, the grayscale value will drop (0 = black, 255 = white) as browning worsens—so lower average grayscale = more browning. That part of your initial approach is spot-on.

Now, about using histograms to find average darkness:

• Absolutely! The histogram’s average intensity (called Mean in Photoshop’s stats) is exactly what you need. Here’s how to access it:
  1. First, critical step: make sure all your apple slice photos are taken under identical conditions—same lighting, camera angle, distance, background. Any variation here will skew your results way more than the tool itself.
  2. Open your image, and use the Crop Tool or Marquee Tool to isolate just the apple slice (exclude the background entirely). You can copy the selected slice to a new layer with Ctrl+J (Windows) or Cmd+J (Mac) to keep things clean.
  3. Either convert the layer to grayscale (Image > Mode > Grayscale) or stick with RGB—both work, but grayscale simplifies things visually.
  4. Open the Histogram panel (Window > Histogram). Click the menu icon in the top-right corner of the panel and select Show Statistics.
  5. Look for the Mean value in the stats panel. This is the average brightness (grayscale value) of all pixels in your selected slice. Lower numbers mean darker (more browned) flesh.

A few pro tips to make your measurements more reliable:

• Avoid adjusting brightness/contrast or any other color settings on your original photos—keep the raw image data intact for accurate comparisons.
• If your slice has uneven spots (like reflections or small dark blemishes), use the Marquee Tool to select a large, uniform area of the flesh instead of the whole slice.
• For extra precision, use the Color Sampler Tool (press I on your keyboard) to pick 5-10 evenly spaced points on the slice, note their grayscale values, and calculate a manual average. This helps reduce the impact of any weird outliers.

You don’t need to deep-dive into the technical mechanics of grayscale or histograms to make this work—what matters most is consistency in your process. As long as you follow the same steps for every apple slice, the relative differences in the Mean values will give you a clear, quantifiable way to compare how well each browning prevention method works.

备注：内容来源于stack exchange，提问作者Clueless