Is the vertical-align attribute invalid? What is the root cause of the failure of vertical centering of the picture

The truth about the failure of vertical-align attribute: the problem of vertical centering of elements in the line

Many front-end developers often fail when using the vertical-align attribute to vertically center images. This article will conduct a case analysis to deeply analyze the root cause of vertical-align failure and explain why the "lower" of elements in the line will lead to failure of vertical centering.

Problem: Image elements cannot be vertically centered through vertical-align .

The key is to understand the layout characteristics of the elements within the line and the working mechanism of vertical-align . The so-called "ghost blank node" actually refers to the actual height of elements within the line. The vertical-align attribute acts on the elements in the row and is aligned vertically based on the height of the elements in the row.

If line-height is not set, the height of the inline element is usually the same as the height of the image. At this time, vertical-align cannot achieve vertical centering because the image has occupied the height of elements in the entire row. However, if line-height is set and line-height value is greater than the image height, the element height in the line will be equal to line-height value. The image is vertically aligned relative to the height of the larger in-line element, thereby achieving vertical centering.

Therefore, setting line-height value is crucial. vertical-align can only work effectively when line-height value is large enough. "The height of the element in the line is too small" is the root cause of vertical-align failure. This is directly related to the nature of the Inline Formatting Context: the vertical alignment of in-line elements depends entirely on their own height.

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