13 files declare their use of ImageInterface in Drupal 8

AjaxTestImageEffect.php in core/modules/image/tests/modules/image_module_test/src/Plugin/ImageEffect/AjaxTestImageEffect.php

ConvertImageEffect.php in core/modules/image/src/Plugin/ImageEffect/ConvertImageEffect.php

CropImageEffect.php in core/modules/image/src/Plugin/ImageEffect/CropImageEffect.php

DesaturateImageEffect.php in core/modules/image/src/Plugin/ImageEffect/DesaturateImageEffect.php

ImageEffectInterface.php in core/modules/image/src/ImageEffectInterface.php

NullTestImageEffect.php in core/modules/image/tests/modules/image_module_test/src/Plugin/ImageEffect/NullTestImageEffect.php

ResizeImageEffect.php in core/modules/image/src/Plugin/ImageEffect/ResizeImageEffect.php

responsive_image.module in core/modules/responsive_image/responsive_image.module

Responsive image display formatter for image fields.

RotateImageEffect.php in core/modules/image/src/Plugin/ImageEffect/RotateImageEffect.php

ScaleAndCropImageEffect.php in core/modules/image/src/Plugin/ImageEffect/ScaleAndCropImageEffect.php

ScaleImageEffect.php in core/modules/image/src/Plugin/ImageEffect/ScaleImageEffect.php

ToolkitGdTest.php in core/tests/Drupal/KernelTests/Core/Image/ToolkitGdTest.php

UriDependentTestImageEffect.php in core/modules/image/tests/modules/image_module_test/src/Plugin/ImageEffect/UriDependentTestImageEffect.php