66 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s 66 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s The Plug-in function PIPHP_ImageResize($image, $w, $h) { $oldw = imagesx($image); $oldh = imagesy($image); $temp = imagecreatetruecolor($w, $h); imagecopyresampled($temp, $image, 0, 0, 0, 0, $w, $h, $oldw, $oldh); return $temp; } Make Thumbnail Many thumbnail programs exist that will take a large image and reduce it to a thumbnail for you, often supporting working in batches. But what about turning user uploaded images into thumbnails? Obviously you don’t want to simply send a large image to the browser and have HTML resize it since the quality wouldn’t be great, and your bandwidth would go through the roof. So you need something to handle this process on the fly, which is where this plug-in comes in handy. With it you specify a source image and the maximum dimensions allowed for the new thumbnail. The function will then resize the image, retaining the aspect ratio, so that whichever of the height or width is the larger dimension is then set to the new maximum size, and the other is reduced in proportion. Figure 4-3 shows the smiley face image, from the previous plug-in, used as a thumbnail source for two smaller thumbnail images. FIGURE 4-3 The Make Thumbnail plug-in has been used to make two different thumbnails of a smiley face. 13 C h a p t e r 4 : I m a g e H a n d l i n g 67 C h a p t e r 4 : I m a g e H a n d l i n g 67 About the Plug-in This plug-in accepts an image to be converted into a thumbnail and the new maximum width or height. It takes these arguments: � $image A GD image to be transformed � $max The new maximum width or height (whichever is the greater dimension) Variables, Arrays, and Functions $w Integer representing the image’s current width $h Integer representing the image’s current height $thumbw Integer representing the thumbnail’s new width $thumbh Integer representing the thumbnail’s new height How It Works To create the new thumbnail image, this plug-in accepts a GD image object and then sets $w and $thumbw to its width, and $h and $thumbh to its height. Next it looks at these values to find out which dimension is the larger. If $w is greater than $h, then the image is wider than it is high, so the new width will take the value in $max, and thus $thumbh, the smaller thumbnail height, is set to the maximum dimension value of $max divided by the original image’s width, in $w, and multiplied by its height, in $h. So, for example, if the original image’s width is 1200 pixels, the height is 1000, and the new maximum dimension size is 100 pixels, the following formula is applied: Thumbnail Height = 100 / 1200 × 1000 This becomes: Thumbnail Height = 0.0833 × 1000 Which results in: Thumbnail Height = 83.33 Therefore, if the new width is to be 100 pixels, then the new height must be 83.33 pixels (which will be rounded down to 83). Similarly, if the height is greater than the width, then the height will be set to the value in $max and the width will be set to a percentage of that height. In both cases, a test is made to see whether $max is already smaller than the new height or width, because if it’s not then the image is already of thumbnail size. A final test is made for whether the value in $max is less than that in $h. If so this means that the requested new image size is smaller than the original, and that the width and height required are equal, so $thumbw and $thumbh are both set to the value in $max. In this case, the thumbnail will be square and so both $thumbw and $thumbh are assigned the value in $max. With all the calculations over, the previous plug-in, PIPHP_ImageResize(), is called to perform the resizing. The image that is returned from this plug-in is returned to the calling code. 68 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s 68 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s How to Use It To create a thumbnail, you pass the function PIPHP_MakeThumbnail() a GD image object and the maximum value of the greater dimension for the thumbnail. For example, the following code loads in the image in test.jpg using the imagecreatefromjpeg() function, and then passes it to the plug-in, along with a maximum dimension of 100. The function then returns the new thumbnail to the string variable $thumb, which is then saved to the file thumb.jpg using the imagejpeg() function. $image = imagecreatefromjpeg("test.jpg"); $thumb = PIPHP_MakeThumbnail($image, 100); imagejpeg($thumb, "thumb.jpg"); You can also output the thumbnail straight to the browser by first sending the correct header, like this: $image = imagecreatefromjpeg("test.jpg"); header("Content-type: image/jpeg"); imagejpeg(PIPHP_MakeThumbnail($image, 100)); Because this plug-in also uses the PIPHP_ImageResize() function, you will need both of these in (or included by) your program file. The Plug-in function PIPHP_MakeThumbnail($image, $max) { $thumbw = $w = imagesx($image); $thumbh = $h = imagesy($image); if ($w > $h && $max < $w) { $thumbh = $max / $w * $h; $thumbw = $max; } elseif ($h > $w && $max < $h) { $thumbw = $max / $h * $w; $thumbh = $max; } elseif ($max < $w) { $thumbw = $thumbh = $max; } return PIPHP_ImageResize($image, $thumbw, $thumbh); } Image Alter The PHP GD library is so powerful that it can perform a variety of image manipulations you would normally only find in a graphics program. In fact, you could probably build quite an advanced image editor using them. This plug-in goes someway towards that by providing 14 C h a p t e r 4 : I m a g e H a n d l i n g 69 C h a p t e r 4 : I m a g e H a n d l i n g 69 14 different image transformations you can apply to your graphics, and Figure 4-4 shows just one of these, Edge Detect, in use. About the Plug-in This plug-in accepts an image to be converted, along with the transformation required. It takes these arguments: � $image A GD image to be transformed � $effect The transformation to apply, between 1 and 14: $effect Action 1 Sharpen 2 Blur 3 Brighten 4 Darken 5 Increase contrast 6 Decrease contrast 7 Grayscale 8 Invert 9 Increase red 10 Increase green 11 Increase blue 12 Edge detect 13 Emboss 14 Sketchify FIGURE 4-4 This photograph has been modified by passing it through the Image Alter plug-in. 70 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s 70 P l u g - i n P H P : 1 0 0 P o w e r S o l u t i o n s Variables, Arrays, and Functions � None How It Works To select between the available transformation effects, the plug-in uses a large switch statement that supports 14 different cases to apply to the supplied GD image object. It then calls the relevant function with the required parameters and returns the new image. How to Use It To perform an Edge Detect transformation on a file called photo.jpg, as shown in Figure 4-4, you could use the following code, which will load a GD image object using the imagecreatefromjpeg() function, and save the transformed image with the function imagejpeg(), using the filename photo2.jpg: $image = imagecreatefromjpeg("photo.jpg"); $copy = PIPHP_ImageAlter($image, 12); imagejpeg($copy, "photo2.jpg"); Or to output the transformed image directly to a browser, you could use the following code to output the correct header first: $image = imagecreatefromjpeg("photo.jpg"); header("Content-type: image/jpeg"); imagejpeg(PIPHP_ImageAlter($image, 12)); The Plug-in function PIPHP_ImageAlter($image, $effect) { switch($effect) { case 1: imageconvolution($image, array(array(-1, -1, -1), array(-1, 16, -1), array(-1, -1, -1)), 8, 0); break; case 2: imagefilter($image, IMG_FILTER_GAUSSIAN_BLUR); break; case 3: imagefilter($image, IMG_FILTER_BRIGHTNESS, 20); break; case 4: imagefilter($image, IMG_FILTER_BRIGHTNESS, -20); break; case 5: imagefilter($image, IMG_FILTER_CONTRAST, -20); break; case 6: imagefilter($image, IMG_FILTER_CONTRAST, 20); break; case 7: imagefilter($image, IMG_FILTER_GRAYSCALE); break; case 8: imagefilter($image, IMG_FILTER_NEGATE); break; case 9: imagefilter($image, IMG_FILTER_COLORIZE, 128, 0, 0, 50); break; . imagejpeg(PIPHP_MakeThumbnail($image, 100) ); Because this plug- in also uses the PIPHP_ImageResize() function, you will need both of these in (or included by) your program file. The Plug- in function PIPHP_MakeThumbnail($image,. Functions $w Integer representing the image’s current width $h Integer representing the image’s current height $thumbw Integer representing the thumbnail’s new width $thumbh Integer representing the. if the original image’s width is 1200 pixels, the height is 1000 , and the new maximum dimension size is 100 pixels, the following formula is applied: Thumbnail Height = 100 / 1200 × 1000 This