Blob detection is the process of identifying the pixels that make up each peak. Once the blobs of pixels are detected, they can be visualized and analyzed. The position (i.e., the retention times in each dimension) of each blob is related to the physical properties the chemical that produced the blob, so the position of a blob is useful in identifying each chemical in a sample. The sum of the pixel values in each blob is related to the quantity of the chemical that produced it, so the sum of pixel values of a blob is useful in quantifying each chemical in a sample.
Step 1: Select Detect Blobs from the Filters
menu on the Image Viewer menu bar or click the Blob
Detection button on the Image Viewer tool bar.
GC Image detects the blobs and creates a blob table that can be
analyzed and reported.
The blobs are highlighted graphically in the Viewport of the
Image Viewer and in other tools according to blob display
configuration.
Step 1: Select Configure Settings from the Configure menu of the Image Viewer. GC Image launches a pop-up with various configuration dialog panes.
Step 2: Select the Blob Detection configuration pane.
Step 3: Set the number of detection algorithm, smoothing window, distribution, and filter parameters. Click the OK button. See chapter Preprocessing for a description of the blob detection algorithm and parameters.
Step 1: Select Configure Settings from the Configure menu of the Image Viewer. GC Image launches a pop-up with various configuration dialog panes.
Step 2: Select the Blob Display configuration pane.
Step 3: Set what blobs to show, how to show blobs, whether to show internal standard associations, and colors. Click the OK button.
Step 1: Set the cursor mode to one of the blob selection
modes (point, line, rectangle, or polygon) from the graphics cursor
mode selector on the Image Viewers palette.
Step 2: Select blob(s) depending on the blob selection mode.
- In pixel blob-selection mode, move the cursor inside the border of a blob and click the left mouse-button. Select additional blobs for the selection set by holding the control key during the click of the left mouse-button while the cursor is inside the next blob to be selected.
- In line blob-selection mode, move the cursor to one side of a series of blobs, depress the left mouse-button, move the cursor to the other side of the series (defining a line through the series), and release the mouse button. All blobs crossed by the line will be selected.
- In rectangle blob-selection mode, move the cursor to a point above (or below) and left (or right) of all blobs to be selected, depress the left mouse-button, move the cursor below (or above) and right (or left) of all the blob peaks to be selected (defining a bounding box), and release the mouse button. All blobs with the peak pixel in the rectangle will be selected.
- In polygon blob-selection mode, move the cursor to a point near the blobs to be selected, click the left mouse-button, repeatedly move the cursor around the blobs to be selected and click the left mouse-button (drawing a polygon), and double click the left mouse-button (to close the polygon). All blobs with the peak pixel in the polygon will be selected.
GC Image graphically highlights selected blobs in the Viewport
of the Image Viewer according to blob display configuration.
Step 1: Set the cursor mode to select blob mode.
Step 2: Select the Select All item from the Edit menu. GC Image will select all blobs.
Step 1: Select a focal blob using the blob selection cursor mode.
Step 2: Select Edit Blobs from the Edit menu on
the Image Viewer menu bar or the Edit Blobs button on
the Image Viewer tool bar.
GC Image launches Edit Blobs.
Step 3: Navigate the cross-hairs over the blob (or region) to be edited by click-and-drag in the image pane of Edit Blobs, Shift-Click in the image pane of Edit Blobs, or clicking the arrow navigation buttons.
Step 4: Use the operation buttons to split the blob vertically, split the blob horizontally, merge the blob with an adjacent blob, exclude the blob, or add a new blob.
Step 1: Select the blob(s) to be excluded.
Step 2: Click the Delete / Exclude Object button. Confirmation is required.
Step 1: Select the Draw Blob cursor mode.
Step 2: Click down on the mouse left-button, draw the cursor around the border of the blob (without crossing the line drawn or other blobs), and release the button to close the shape.