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GetPixelBandValue

Updated
globalmapper.GetPixelBandValue(GM_LayerHandle_t32 aLayer, sint32 aRow, sint32 aCol, sint32 aBand) → GM_Error_t32, sint32

Retrieves the band value at a given pixel location in the provided layer. If the layer does not contain a valid sample at the provided pixel location (i.e. it is a “no data” or transparent value), GM_Error_NoDataAtLocation will be returned. Use this to access the raw values from high-bit depth and multi-band imagery layers.

Parameters:

  • aLayer (GM_LayerHandle_t32) – Layer to get color from

  • aRow (sint32) – Y coord of pixel (0 is topmost)

  • aCol (sint32) – X coord of pixel (0 is leftmost)

  • aBand (sint32) – Band to get value for (0-based, so first band is 1)

Returns:

Error Code

Return type:

GM_Error_t32

Returns:

Color of pixel at location

Return type:

sint32


Note: To get pixel row/col data, you can select a point feature in Global Mapper:

Right-click -> Attribute/Style Functions -> Add Pixel Coordinates to Selected Point(s)

Example

The following is an example of GetPixelBandValue.

import os
import globalmapper as gm

import_dir = "Z:/GM-20069/single_function_sample_data/"
# Close all layers that may be open
layers_are_open = gm.GetLoadedLayerList()
if layers_are_open:
    arr_ptr, arr_size = layers_are_open
    initial_layers = gm.GM_LayerHandle_array_frompointer(arr_ptr)
    for i in range(arr_size):
        gm.CloseLayer(initial_layers[i])

err_LoadLayerList, array_pointer, array_size_param = gm.LoadLayerList(
    os.path.join(import_dir, "Augusta.jpg"),
    gm.GM_LoadFlags_HideAllPrompts,
)

# Get handle for the loaded layers
arr_ptr, arr_size = gm.GetLoadedLayerList()
layers_array = gm.GM_LayerHandle_array_frompointer(arr_ptr)
layers_list = gm.carray_to_list(layers_array, arr_size)

### START SAMPLE
err_GetPixelBandValue, pixel_colorR = gm.GetPixelBandValue(
    layers_list[0], 277, 878, 0
)

### END SAMPLE

assert (
    gm.GM_Error_None == err_LoadLayerList
), f"LoadLayerList: Expected {gm.GM_Error_None}, got {err_LoadLayerList}"
assert (
    gm.GM_Error_None == err_GetPixelBandValue
), f"GetPixelBandValue: Expected {gm.GM_Error_None}, got {err_GetPixelBandValue}"