3.1   Reading Images From Files

Especially during prototyping phase you often have a set of sample image files to work from. HDevelop supports an extensive variety of image formats that can be loaded directly (see read_image in the Reference Manual).

Drag-and-Drop

The easiest way to read an image is to simply drag it from a file browser to the HDevelop window and drop it there. When the file is dropped, HDevelop opens the dialog Read Image (see figure 3.1).

Figure 3.1: Read Image Dialog.

This dialog displays the full path of the image and automatically proposes a variable name derived from the file name. This name can be edited, or another iconic variable name from the current program can be selected from the drop-down list.

Furthermore, a preview of the image and basic image properties are displayed in the dialog (width, height, color type, and number of channels). If you picked the wrong image, you can select another one from the same directory by pressing the button next to the file name. This will open a file browser native to the operating system. On Windows, you may be able to switch to thumbnail view in this dialog. When another image is selected, the dialog is updated accordingly.

When you click the button OK, the instruction read_image is added to the current program. With the setting of Insert Position you determine where the instruction will be put: At the IC or the PC. If you changed your mind about reading the selected image at all, click Cancel.

Drag-and-Drop of Multiple Images

You can also drag multiple images or directories containing multiple images to HDevelop. HDevelop will then open an image acquisition assistant with the images preselected. See section “Image Acquisition Assistant” for further information.

Images From Selected Directories

Select File ▹ Read Image... to get the dialog described above.

File Name  

You can enter the name of an image file into this field. A relative file name is looked up in several directories in that order:

1. The current working directory (., a single dot) is the directory HDevelop was started from.
2. The subdirectory images of the directory specified by the environment variable HALCONROOT.
3. The directories specified by the environment variable HALCONIMAGES.
4. The directories used in previous invocations of Read Image....

The first matching image file is displayed as a thumbnail preview along with its width, height, color type and number of channels.

Alternatively, open a file selection dialog by selecting a predefined directory from the File Name combo box or clicking the browse button. The latter will start browsing in the current working directory, or in the last used directory. Depending on the operating system you may be able to switch to a thumbnail view in the file selection dialog.

Variable Name  

HDevelop suggests a variable name derived from the selected file name. You may adopt or edit this name. If you want to use a name of an already created iconic variable, this combo box offers you all known iconic variable names. Simply click the arrow on the right side of the combo box to select a variable name. Note that the reuse of a variable deletes the old content and replaces it with the new image.

After selecting a file name, click OK to load the image into HDevelop. The operator read_image is inserted at the specified insert position (IC or PC). The specified iconic variable is updated in the variable window and the image is displayed in the active graphics window. Clicking Cancel aborts the operation.

By default, an absolute path to the selected image is inserted. You can instruct HDevelop to use relative path names (see General Options ▹ General Options in the preferences).