@wordpress/block-library/src/image/editor.scss

.wp-block-image {
	position: relative;

	&.is-transient img {
		opacity: 0.3;
	}

	figcaption img {
		display: inline;
	}

	// Shown while image is being uploaded
	.components-spinner {
		position: absolute;
		top: 50%;
		left: 50%;
		margin-top: -9px;
		margin-left: -9px;
	}
}

// This is necessary for the editor resize handles to accurately work on a non-floated, non-resized, small image.
.wp-block-image .components-resizable-box__container {
	display: inline-block;

	img {
		display: block;
		width: 100%;
	}
}

// Ensure the resize handles are visible when the image is focused.
.wp-block-image.is-focused .components-resizable-box__handle {
	display: block;
	z-index: z-index(".block-library-image__resize-handlers");
}

.block-editor-block-list__block[data-type="core/image"][data-align="center"] {
	.wp-block-image {
		margin-left: auto;
		margin-right: auto;
	}

	&[data-resized="false"] .wp-block-image > div {
		margin-left: auto;
		margin-right: auto;
	}
}

.edit-post-sidebar .block-library-image__dimensions {
	margin-bottom: 1em;

	.block-library-image__dimensions__row {
		display: flex;
		justify-content: space-between;

		.block-library-image__dimensions__width,
		.block-library-image__dimensions__height {
			margin-bottom: 0.5em;

			// Fix the text and placeholder text being misaligned in Safari
			input {
				line-height: 1.25;
			}
		}

		.block-library-image__dimensions__width {
			margin-right: 5px;
		}

		.block-library-image__dimensions__height {
			margin-left: 5px;
		}
	}
}

.block-editor-block-list__block[data-type="core/image"] .block-editor-block-toolbar .block-editor-url-input__button-modal {
	position: absolute;
	left: 0;
	right: 0;
	margin: -$border-width 0;

	@include break-small() {
		margin: -$border-width;
	}
}

// Although the float markup is different in the editor compared to the frontend,
// this CSS uses the same technique to allow floats in a wide images context.
// That is, the block retains its centering and max-width, and a child inside
// is floated instead of the block itself.
[data-type="core/image"][data-align="center"],
[data-type="core/image"][data-align="left"],
[data-type="core/image"][data-align="right"] {
	.block-editor-block-list__block-edit {
		figure {
			margin: 0;
			display: table;
		}

		// This maps to the figcaption on the frontend.
		.block-editor-rich-text {
			display: table-caption;
			caption-side: bottom;
		}
	}
}

[data-type="core/image"][data-align="wide"],
[data-type="core/image"][data-align="full"] {
	figure img {
		width: 100%;
	}
}

// This is similar to above but for resized unfloated images only, where the markup is different.
[data-type="core/image"] .block-editor-block-list__block-edit figure.is-resized {
	margin: 0;
	display: table;

	// This maps to the figcaption on the frontend.
	.block-editor-rich-text {
		display: table-caption;
		caption-side: bottom;
	}
}