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Diffstat (limited to 'dmagick/c/layer.d')
| -rw-r--r-- | dmagick/c/layer.d | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/dmagick/c/layer.d b/dmagick/c/layer.d index ccf73b5..8928453 100644 --- a/dmagick/c/layer.d +++ b/dmagick/c/layer.d @@ -17,24 +17,202 @@ extern(C) PreviousDispose = 3 } + /** + * Determines image operation to apply to ordered sequence of images. + */ enum ImageLayerMethod { + /** */ UndefinedLayer, + + /** + * Apply the GIF disposal methods set in the current image sequence + * to form a fully defined animation sequence without, as it should + * be displayed. Effectively converting a GIF animation into + * a 'film strip' like animation. + */ CoalesceLayer, + + /** + * Crop the second and later frames to the smallest rectangle that + * contains all the differences between the two images. No GIF + * disposal methods are taken into account. + * + * This does not preserve a animation's normal working, especially + * when a animation used GIF disposal methods + * such as 'Previous' or 'Background'. + */ CompareAnyLayer, + + /** + * As CompareAnyLayer but crop to the bounds of any opaque pixels + * which become transparent in the second frame. That is the + * smallest image needed to mask or erase pixels for the next frame. + */ CompareClearLayer, + + /** + * As CompareAnyLayer but crop to pixels that add extra color to + * the next image, as a result of overlaying color pixels. That is + * the smallest single overlaid image to add or change colors. + * + * This can, be used with the -compose alpha composition method + * 'change-mask', to reduce the image to just the pixels that need + * to be overlaid. + */ CompareOverlayLayer, + + /** + * This is like CoalesceLayer but shows the look of the animation + * after the GIF disposal method has been applied, before the next + * sub-frame image is overlaid. That is the 'dispose' image that + * results from the application of the GIF disposal method. This + * allows you to check what is going wrong with a particular + * animation you may be developing. + */ DisposeLayer, + + /** + * Optimize a coalesced animation into GIF animation using a number + * of general techniques. This is currently a short cut to apply + * both the OptimizeImageLayer and OptimizeTransLayer methods + * but will expand to include other methods. + */ OptimizeLayer, + + /** + * Optimize a coalesced animation into GIF animation by reducing + * the number of pixels per frame as much as possible by attempting + * to pick the best GIF disposal method to use, while ensuring the + * result will continue to animate properly. + * + * There is no guarantee that the best optimization will be found. + * But then no reasonably fast GIF optimization algorithm can do + * this. However this does seem to do better than most other GIF + * frame optimizers seen. + */ OptimizeImageLayer, + + /** + * As OptimizeImageLayer but attempt to improve the overall + * optimization by adding extra frames to the animation, without + * changing the final look or timing of the animation. The frames + * are added to attempt to separate the clearing of pixels from the + * overlaying of new additional pixels from one animation frame to + * the next. If this does not improve the optimization (for the next + * frame only), it will fall back to the results of the previous + * normal OptimizeImageLayer technique. + * + * There is the possibility that the change in the disposal style + * will result in a worsening in the optimization of later frames, + * though this is unlikely. In other words there no guarantee that + * it is better than the normal 'optimize-frame' technique. + */ OptimizePlusLayer, + + /** + * Given a GIF animation, replace any pixel in the sub-frame overlay + * images with transparency, if it does not change the resulting + * animation by more than the current fuzz factor. + * + * This should allow a existing frame optimized GIF animation to + * compress into a smaller file size due to larger areas of one + * (transparent) color rather than a pattern of multiple colors + * repeating the current disposed image of the last frame. + */ OptimizeTransLayer, + + /** + * Remove (and merge time delays) of duplicate consecutive images, + * so as to simplify layer overlays of coalesced animations. Usually + * this is a result of using a constant time delay across the whole + * animation, or after a larger animation was split into smaller + * sub-animations. The duplicate frames could also have been used as + * part of some frame optimization methods. + */ RemoveDupsLayer, + + /** + * Remove any image with a zero time delay, unless ALL the images + * have a zero time delay (and is not a proper timed animation, a + * warning is then issued). In a GIF animation, such images are + * usually frames which provide partial intermediary updates between + * the frames that are actually displayed to users. These frames are + * usually added for improved frame optimization in GIF animations. + */ RemoveZeroLayer, + + /** + * Alpha Composition of two image lists, separated by a "null:" + * image, with the destination image list first, and the source + * images last. An image from each list are composited together + * until one list is finished. The separator image and source image + * lists are removed. + * + * The geometry offset is adjusted according to gravity in + * accordance of the virtual canvas size of the first image in each + * list. Unlike a normal composite operation, the canvas offset is + * also added to the final composite positioning of each image. + * + * If one of the image lists only contains one image, that image is + * applied to all the images in the other image list, regardless of + * which list it is. In this case it is the image meta-data of the + * list which preserved. + */ CompositeLayer, + + /** + * As FlattenLayer but merging all the given image layers into a + * new layer image just large enough to hold all the image without + * clipping or extra space. The new image's virtual offset will + * prevere the position of the new layer, even if this offset is + * negative. the virtual canvas size of the first image is preserved. + * + * Caution is advised when handling image layers with negative + * offsets as few image file formats handle them correctly. + */ MergeLayer, + + /** + * Create a canvas the size of the first images virtual canvas using + * the current background color, and compose each image in turn onto + * that canvas. Images falling outside that canvas will be clipped. + * Final image will have a zero virtual canvas offset. + * + * This is usually used as one of the final 'image layering' + * operations overlaying all the prepared image layers into a + * final image. + * + * For a single image this method can also be used to fillout a + * virtual canvas with real pixels, or to underlay a opaque color + * to remove transparency from an image. + */ FlattenLayer, + + /** + * As FlattenLayer but expanding the initial canvas size of the + * first image so as to hold all the image layers. However as a + * virtual canvas is 'locked' to the origin, by definition, image + * layers with a negative offsets will still be clipped by the top + * and left edges. + * + * This method is commonly used to layout individual image using + * various offset but without knowing the final canvas size. The + * resulting image will, like FlattenLayer not have any virtual + * offset, so can be saved to any image file format. This method + * corresponds to mosaic, above. + */ MosaicLayer, + + /** + * Find the minimal bounds of all the images in the current image + * sequence, then adjust the offsets so all images are contained + * on a minimal positive canvas. None of the image data is modified, + * only the virtual canvas size and offset. Then all the images will + * have the same canvas size, and all will have a positive offset, + * at least one image will touch every edge of that canvas with + * actual pixel data, though that data may be transparent. + */ TrimBoundsLayer } |