Скачать или смотреть Save an IPicture to TStream and Display it in Delphi's TImage

Learn how to efficiently save an `IPicture` to a `TStream` and display it in a `TImage` component using Delphi. This guide walks through the necessary steps without unnecessary complexities.
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This video is based on the question https://stackoverflow.com/q/75560588/ asked by the user 'jcaique' ( https://stackoverflow.com/u/19583416/ ) and on the answer https://stackoverflow.com/a/75568581/ provided by the user 'Remy Lebeau' ( https://stackoverflow.com/u/65863/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Save an IPicture to a TStream and Display it in a Delphi TImage

Working with images in Delphi can sometimes lead to confusion, especially when trying to manipulate various types of image formats and Delphi components. One common scenario is needing to take an IPicture, save it to a stream, and then display it directly in a TImage component. If you've found yourself stuck trying to save an image and display it correctly, you're not alone. Let's break down the solution to this problem step-by-step.

Introduction to the Problem

When working with images in Delphi, especially with IPicture, the goal is often to hold this image in memory and render it on a GUI component like TImage. While the OleSavePictureFile function allows you to save images to physical files, this isn't always desirable or efficient. Your goal might instead be to save these images directly in memory for quicker access or other manipulations.

The Key Steps to Follow

A Common Mistake: Stream Position

A common oversight when working with streams is failing to reset the stream's position after writing to it. If the position is not reset, reading from the stream will result in no actual data being available, leading to blank outputs on your TImage. Remember, after writing to a stream, always:

Set the stream position back to 0 before reading from it again.

Alternative Approach: Use TOleGraphic Directly

In most cases, there's a more straightforward approach than saving to a stream and then loading the data into a TBitmap or TImage. Since TOleGraphic is a descendant of TGraphic, it can be directly assigned to a TImage component. Here’s how you can do it:

Example Code

[[See Video to Reveal this Text or Code Snippet]]

Commentary on the Code

Conversion of IPicture: The IPicture is obtained through whatever method you are using (e.g., DPBiometria.DPSC.ConvertToPicture(pSample)).

Using TOleGraphic: The TOleGraphic serves as a bridge from IPicture to be appropriately displayed in a TImage.

Memory Management: The TRY-FINALLY block ensures that the memory allocated for TOleGraphic is properly released after use.

Conclusion

By directly using TOleGraphic, you simplify the process of displaying images significantly. Not only does this avoid the complexity of stream management, but it also enhances the performance of your application by reducing unnecessary file operations. Remember, efficiency in coding isn't just about writing functioning code; it’s about creating code that is easy to maintain and understand.

If you follow the methodology outlined in this guide, managing images in Delphi will become an easier and more streamlined part of your development process. Happy coding!