Processing 2D images and textures-create a texture, define the color of each pixel, and save the texture to a file

Problem

You want to create a new texture and manually define the color of each pixel. It is useful when you want users to create a new image or generate a manual image such as a deep texture.

You want to store this texture in a file, such as generating a game or for debugging purposes.

Solution

Setting the color of an image and saving the texture in the selected format to a file is directly supported by xNa framework.

You can call the setdata method of the texture to change its content. This method takes an array containing the color values of each pixel as a parameter.

You can use the Save method of texture to save it to a file.

Working Principle

First, create an array to save the color of each pixel in the image:

 
Int texturewidth = 512; int textureheight = 512; color [] texturecolors = new color [texturewidth * textureheight]; int I = 0; For (INT ver = 0; ver <textureheight; ver ++) for (INT Hor = 0; Hor <texturewidth; Hor ++) {float Red = (float) Hor/(float) texturewidth; float Green = 0; float Blue = (float) Ver/(float) textureheight; float alpha = 1; texturecolors [I ++] = new color (New vector4 (red, green, blue, alpha ));}
 

AboveCodeFirst, create an array that stores colors for a texture with a resolution of 512x512. Then fill each pixel with two for loops. With this filling order, you first traverse pixels from the upper left corner, from left to right, and from top to bottom.

Finally, you need to create a texture and load the content in the array to the texture memory:

 
Texture2d newtexture = new texture2d (device, texturewidth, textureheight, 1, textureusage. None, surfaceformat. Color );
 

Then, after device and image resolution, you need to specify the number of mipmap (see the following notes ). The next parameter allows you to set textureusage. By selecting textureusage. autogeneratemipmap, xNa will automatically generate the number of your specified mipmaps. Remember, if you want to use mipmap, the width and height of the image must be an integer power of 2.

Note:A mipmapped image contains multiple resolutions of an image, which is useful in many cases. When drawing a 3D scene, if a box with textures is so far away from the camera that there is only one pixel in the window. To determine the color of the box, the video card still needs to calculate the texture coordinate from which to sample the texture. When you move the camera a little bit, the texture coordinates may be slightly different, but may correspond to a completely different color in the texture. As a result, a camera changes the color of the box, causing pixel flashes on the screen. One solution is to store multiple versions with different resolutions in the image. For a 64x64 pixel image, If you enable mipmapping, xNa will also create a 32x32, 16x16, 8x8, 4x4, 2x2 until 1x1 version in the image, A single pixel of a 1 × 1 image is the color of the entire texture. Now, in the long box, xNa uses the image's 1x1. In this way, changes in texture coordinates will not lead to changes in color, and flickering pixels will remain unchanged!

The last parameter specifies the pixel format in the texture, which is required to allocate enough memory for the xNa to store the texture. In addition, this is the expected format when you get the value in the texture. When you write data to the texture, you must provide the data in this format.

Finally, simply store the color array in the texture:

 
Newtexture. setdata <color> (texturecolors );
 

It is easier to save the texture to a file:

 
Mytexture. Save ("savedtexture.jpg", imagefileformat. jpg );
 

The last parameter specifies the File compression format to ensure that the file extension corresponds to this format. Otherwise, it will be troublesome to try to open the file from an external image browser.

When the code is run, the file is created to the same location as the executable file. The default value is in the \ bin \ x86 \ debug folder.

Code

The following code creates a texture, fills it with color data, and returns the texture:

Private texture2d definetexturecolors () {int texturewidth = 512; int textureheight = 512; color [] texturecolors = new color [texturewidth * textureheight]; int I = 0; for (INT ver = 0; ver <textureheight; ver ++) for (INT Hor = 0; Hor <texturewidth; Hor ++) {texturecolors [I ++] = new color (New vector4 (float) Hor/(float) texturewidth, 0, (float) Ver/(float) textureheight, 1);} texture2d newtexture = new texture2d (device, texturewidth, textureheight, 1, resourceusage. none, surfaceformat. color); newtexture. setdata <color> (texturecolors); Return newtexture ;}
 

This method needs to be called from the loadcontent method because it requires device instantiation:

 
Protected override void loadcontent () {Device = graphics. graphicsdevice; spritebatch = new spritebatch (graphicsdevice); mytexture = definetexturecolors (); mytexture. save ("savedtexture.jpg", imagefileformat. JPG );}