// 现在我们先画一条线吧。画线的函数是这样的： // imageline (int im, int x1, int y1, int x2, int y2, int col); // 第一个参数im，就是图象的ID，后面的 x1,y1,x2,y2，不用说了， // 是起点(x1,y1) 终点(x2,y2)的坐标呀！（图象的左上角坐标是 (0,0) ） // 最后一个参数是什么呀？是颜色！GD要求针对图象定义颜色，用定义的这些颜色来作图。 // 为什么要针对图象定义颜色？我猜测，是为了GIF、PNG等图象用之做“调色板”的。 // 这牵扯到图象本身的知识，这里不赘述了。 // 所以，画线之前，我们还要先定义颜色（真麻烦）。
// $col_red = ImageColorAllocate($im, 255,192,192); // This function has four parameters, the first $im... Do I still need to say it every time? I won’t say it next time! // The next three parameters are the red (R), green (G), and blue (B) components of the color to be defined, between 0 and 255. // This again involves physics-optics knowledge. The different light components of the three primary colors of red, green and blue, // produce ever-changing colors. The color I defined above is 255 red, 192 green, and 192 blue. // If I'm not mistaken, this is a brighter red. Let's try to draw a line in a moment. // Why wait a while? Because if a picture has only one color, nothing can be seen! // Let’s make the background black first! // Although it is not clearly stated in the manual, I found that the color defined first will be used as the background by default.
$col_black = ImageColorAllocate($im, 0,0,0); // Defines a color. There is no red light, green light, or blue light. Natural black - black. // Then define the color for drawing the line: $col_red = ImageColorAllocate($im, 255,192,192);
// Now you can start drawing the red line: imageline ($im , 10, 20, 45, 85, $col_red); // Don’t worry, you won’t be able to see the image after finishing this sentence.
ImagePNG($im); // This sentence outputs an image. ImagePNG() outputs a png image, ImageJPEG outputs a jpeg image, // ImageGIF outputs a gif image... … // Don’t forget there is a parameter here. If it is displayed on the screen instead of saved as a file, // then omit this parameter - the saved file name. If you want to save it as a file here, // You should write it like this: ImagePNG($im, "test.png"); // If you don’t specify a path, this file will be saved in your web page. in the directory. // If it is JPEG, there is one more parameter, which is JPEG quality (0~100). // If you want to display it on the screen, then ImageJPEG($im,"",80); // If you want to save it, then ImageJPEG($im,"test.jpg",80); // Note that if you want to save this image as a file, // you cannot use Header("Content-type: image/png"); to send the HTTP header that means the image, // Because once this happens, it means you will output the image.
ImageDestroy($im); // Destroy the image in memory to free up memory space. // That’s it: the simplest GD drawing is done.
// Through testing, it was found that the PNG format used to generate this image file only has 131 bytes. // And the JPEG format, even with the worst quality (0), requires 855 bytes, the image quality is too bad to watch. // The highest JPEG quality requires 2360 bytes, but the colors are still not as vivid as when using PNG. // It can be seen that for this kind of image with a small number of colors, using PNG is much more cost-effective than JPEG. ?>
This time I will stop here and I will try to continue writing as soon as possible.
http://www.bkjia.com/PHPjc/508283.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/508283.htmlTechArticleI really don’t dare to say that I am “talking” about the GD library here, because I have only used GD once or twice. Most of the functions have not been touched yet. But Sanbanzhu Xiaodiao enthusiastically asked me for a manuscript, so I had no choice but to...
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