From the course: Exploring C Libraries

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Modifying a PNG image

Modifying a PNG image - C Tutorial

From the course: Exploring C Libraries

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Modifying a PNG image

- [Instructor] With image data from the png file located in the memory you're free to manipulate it, changing pixels in whatever way you prefer. In this code I draw an X over the sample png image, 05_05-image1.png which is included with the exercise files. At line eight I create a png pixel structure which contains the four elements of a pixel in RGBA png image data. Bytes for red, green, blue, and the alpha channel. This structure allows me to create color pixels to place in the image data in memory. At lines 27 and 28 I create two png pixel variables. One for the color black, and another for white. I also create a pointer to use when referencing the pixel data in memory pixel_ptr at line 29. After the image data is read and stored in memory manipulation begins after line 95. First I confirm the image color type, which must be RGBA or the pixel modification looks funky. If the image isn't of the RGBA…

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