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Tracing a selection using the Lasso tool


From:

Photoshop CS3 Extended for BioMedical Research

with Eric Wexler

Video: Tracing a selection using the Lasso tool

In the previous video, we covered using Marquees to create regions of interest or areas of interest. In this video, we are going to use the Lasso tool so we are able to trace around a region of interest. So I will select the Lasso tool and we want to make sure it's the regular Lasso tool, since we are going to manually trace around this vessel. If you are working with me open HE_ NORMAL20x.TIF found in your Chapter 10 Exercise Folder. What you are seeing is a hematoxylin and eosin stained coronary vessel. We want to make sure that any measurements we perform are on the correct measurement scale. So we go to Analysis > Set Measurement Scale and select the 20x Calibration.
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  1. 7m 56s
    1. Welcome
      2m 39s
    2. Disclaimer
      1m 44s
    3. Exercise files
      45s
    4. Understanding Photoshop CS3 Extended
      1m 41s
    5. Understanding which versions are covered
      1m 7s
  2. 20m 30s
    1. Understanding imaging in biomedical research
      5m 15s
    2. Understanding research image workflows
      4m 6s
    3. Understanding image fundamentals
      3m 29s
    4. Understanding image detection
      7m 40s
  3. 16m 47s
    1. Understanding digital images
      5m 28s
    2. Understanding image file types
      6m 33s
    3. Understanding objective imaging
      4m 46s
  4. 22m 1s
    1. Understanding the default workspace
      4m 0s
    2. Creating a custom workspace
      5m 31s
    3. Working with keyboard commands
      4m 20s
    4. Customizing preferences for research
      3m 50s
    5. Understanding the History Log
      4m 20s
  5. 18m 9s
    1. Learning to always work from a copy
      2m 23s
    2. Opening files in Photoshop
      4m 13s
    3. Introduction to Adobe Bridge 2.0
      2m 25s
    4. Using the Adobe Camera Raw Converter
      3m 34s
    5. Using the DICOM Importation interface
      4m 18s
    6. Working with scanned image sets
      1m 16s
  6. 13m 46s
    1. Organizing images
      5m 0s
    2. Applying rank, keywords, and filters
      6m 9s
    3. Working with image stacks
      2m 37s
  7. 27m 54s
    1. Understanding color modes
      4m 27s
    2. Understanding the Info panel
      7m 49s
    3. Reading the Histogram panel
      5m 48s
    4. Understanding color composition with channels
      6m 9s
    5. Comparing multiple images
      3m 41s
  8. 25m 19s
    1. Resizing images
      5m 0s
    2. Resizing the image canvas
      8m 11s
    3. Joining images with compositing
      7m 8s
    4. Using Auto Align and Auto Blend
      2m 5s
    5. Applying a threshold to an image
      2m 55s
  9. 23m 45s
    1. Considering adjustments
      2m 19s
    2. Understanding exposure controls
      1m 7s
    3. Optimizing exposure with Levels
      5m 1s
    4. Optimizing exposure using Curves
      7m 24s
    5. Removing color casts
      3m 3s
    6. Reducing chromatic aberrations
      4m 51s
  10. 25m 41s
    1. Understanding layers
      4m 21s
    2. Working with adjustment layers
      1m 35s
    3. Using layers to compare histological localization
      4m 41s
    4. Optimizing a fluorescent image
      4m 27s
    5. Creating a false-color image
      4m 25s
    6. Working with Smart Objects
      4m 13s
    7. Using selective desaturation
      1m 59s
  11. 1h 0m
    1. Understanding the Analysis menu
      3m 4s
    2. Creating a calibration
      3m 56s
    3. Selecting data points
      3m 0s
    4. Using the Marquee Selection tool to isolate an area of interest
      4m 18s
    5. Tracing a selection using the Lasso tool
      3m 31s
    6. Using the Polygonal Lasso tool
      6m 47s
    7. Using the Magnetic Lasso to create an area of interest
      4m 1s
    8. Working with the Quick Select tool
      4m 11s
    9. Using the Magic Wand
      4m 11s
    10. Creating a noncontiguous selection using the Magic Wand
      1m 54s
    11. Creating a selection using Color Range
      4m 32s
    12. Using the Selection tools for visual dissection
      2m 29s
    13. Using the Count tool
      5m 59s
    14. Using the ruler tool with calibration
      4m 28s
    15. Extracting data from the Measurement Log
      3m 41s
  12. 26m 31s
    1. Adding Scale bars manually
      4m 18s
    2. Adding Scale bars automatically
      5m 20s
    3. Adding text to images
      4m 50s
    4. Adding arrows to images
      6m 29s
    5. Adding vector shapes to images
      2m 57s
    6. Adding borders to images
      2m 37s
  13. 32m 29s
    1. Creating contact sheets
      4m 8s
    2. Combining images for presentation
      9m 35s
    3. Using the Bridge Slide Show feature
      2m 58s
    4. Creating a representative grayscale image
      6m 29s
    5. Using the Print interface
      2m 47s
    6. Integrating images into Microsoft Office files
      6m 32s
  14. 15m 23s
    1. Optimizing a DICOM image
      3m 49s
    2. Creating a DICOM animation
      7m 2s
    3. Annotating and optimizing animation
      4m 32s
  15. 1m 0s
    1. Goodbye
      1m 0s

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Watch the Online Video Course Photoshop CS3 Extended for BioMedical Research
5h 37m Intermediate Jan 25, 2008

Viewers: in countries Watching now:

Veteran pharmaceutical research scientist and member of Adobe's Biomedical Image Advisory Group, Eric J. Wexler shares his experience creating detailed biomedical imaging in Photoshop CS3 Extended for Biomedical Research. Eric shows how to use Photoshop CS3's selection, analysis, and editing tools to evaluate an image's color composition, modify images for research, optimize exposure with levels and curves, transform images with layers, and compensate for acquisition problems and limitations. Eric also explains how to add reference information to images, annotate and optimize DICOM animations, and share finished images with colleagues. Exercise files accompany the tutorials.

NOTE: Actual biological research images are used for this title's examples. Some of these images, including those of internal organs and dissected animals, may be considered graphic or offensive to some viewers. Viewer discretion is strongly advised.

Topics include:
  • Understanding imaging in biomedical research
  • Getting started in Photoshop
  • Organizing digital assets
  • Working with image stacks
  • Evaluating image color and histograms
  • Modifying images for research
  • Compensating for acquisition problems and limitations
  • Adding reference information to images
  • Sharing work
  • Optimizing and creating a DICOM image or animation
Subject:
Photography
Software:
Photoshop
Author:
Eric Wexler

Tracing a selection using the Lasso tool

In the previous video, we covered using Marquees to create regions of interest or areas of interest. In this video, we are going to use the Lasso tool so we are able to trace around a region of interest. So I will select the Lasso tool and we want to make sure it's the regular Lasso tool, since we are going to manually trace around this vessel. If you are working with me open HE_ NORMAL20x.TIF found in your Chapter 10 Exercise Folder. What you are seeing is a hematoxylin and eosin stained coronary vessel. We want to make sure that any measurements we perform are on the correct measurement scale. So we go to Analysis > Set Measurement Scale and select the 20x Calibration.

Now we can always use the Info panel to monitor what calibration setting we have selected. Now with this image, one area that you might want to manually trace around would be the boundary between the adventitia, here this lighter pink color, and the cardio myocytes. This would be very difficult to do in an automated way, so you will have to use some sort of manual tool to actually place the selection. By using the Lasso tool, we have to press our button down and just start tracing. Now we have to hold the button down at all times and we just manually go around the area and here, I am using a mouse as I am drawing, a track path would definitely work out better. Now if I were to let go right now, Photoshop would automatically close the selection. Once you start using this tool you are in it for the entire trace, you can't stop half way through or let go off the mouse or else it will be automatically connect the two ends of a line.

In this case, I am close enough. I am going to let go over the mouse and it closed the boundary and now we have our margin and selection around the adventitia of the coronary vessel. This case, I want to open up the Measurement Log. I will go to Window > Measurement Log. Before I hit Record Measurements, even though I have the correct calibration selected, I want to make sure I have the right data points selected. Now 20x Boxes while I use it for boxes previously, in this case, I am going to use it for an area and that's still an appropriate data point set to use.

I can come down, hit Record Measurements. There is my label, the document, the fact that was our selection versus a count or a ruler, it's in microns and I have an area in microns, the perimeter and the height and the width of a bounding box, not the maximum height or the maximum width and that's an important cautionary tale because that height is from this top, all the way down to this bottom and the width is from right here, all the way across to here where it matches up with this point.

So if there was a square bounding box around the region of interest, this is the height and width of that bounding box. Now if you need fine detail and the region of interest is not too large, you can use the Lasso tool but there is two other Lasso tools. They are more automated, they are easier and quicker to use and I will be demonstrating them in the next two videos.

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