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Description
Feature or enhancement
Tk's photo image has the copy subcommand which supports a number of options,
https://www.tcl.tk/man/tcl8.4/TkCmd/photo.htm#M17
imageName copy sourceImage ?option value(s) ...? Copies a region from the image called sourceImage (which must be a photo image) to the image called imageName, possibly with pixel zooming and/or subsampling. If no options are specified, this command copies the whole of sourceImage into imageName, starting at coordinates (0,0) in imageName. The following op‐ tions may be specified: -from x1 y1 x2 y2 Specifies a rectangular sub-region of the source image to be copied. (x1,y1) and (x2,y2) specify diagonally oppo‐ site corners of the rectangle. If x2 and y2 are not specified, the default value is the bottom-right corner of the source image. The pixels copied will include the left and top edges of the specified rectangle but not the bottom or right edges. If the -from option is not given, the default is the whole source image. -to x1 y1 x2 y2 Specifies a rectangular sub-region of the destination im‐ age to be affected. (x1,y1) and (x2,y2) specify diago‐ nally opposite corners of the rectangle. If x2 and y2 are not specified, the default value is (x1,y1) plus the size of the source region (after subsampling and zooming, if specified). If x2 and y2 are specified, the source region will be replicated if necessary to fill the desti‐ nation region in a tiled fashion. -shrink Specifies that the size of the destination image should be reduced, if necessary, so that the region being copied into is at the bottom-right corner of the image. This option will not affect the width or height of the image if the user has specified a non-zero value for the -width or -height configuration option, respectively. -zoom x y Specifies that the source region should be magnified by a factor of x in the X direction and y in the Y direction. If y is not given, the default value is the same as x. With this option, each pixel in the source image will be expanded into a block of x x y pixels in the destination image, all the same color. x and y must be greater than 0. -subsample x y Specifies that the source image should be reduced in size by using only every xth pixel in the X direction and yth pixel in the Y direction. Negative values will cause the image to be flipped about the Y or X axes, respectively. If y is not given, the default value is the same as x. -compositingrule rule Specifies how transparent pixels in the source image are combined with the destination image. When a compositing rule of overlay is set, the old contents of the destina‐ tion image are visible, as if the source image were printed on a piece of transparent film and placed over the top of the destination. When a compositing rule of set is set, the old contents of the destination image are discarded and the source image is used as-is. The de‐ fault compositing rule is overlay.The Tkinter wrapper provides threePhotoImage methodscopy(),zoom() andsubsample() which implement only-zoom and-subsample options (but not their combination) and the call without options. They also have a different semantic, because always return a new image, without possibility to change the part of the existing image.
I propose to add a new method which supports all options and has closer to the origin semantic. Since the namecopy() is already used, the preliminary name of the new method iscopy_replace(). It replaces a part of this image with a part of the specified image, possible with zooming and/or subsampling.
It is possible also to add new options to existing methods if they make sense:from_ to all three of them, andzoom andsubsample to copy.
Recent discussion:https://discuss.python.org/t/add-additional-options-for-the-tkinters-photoimage-copy-method/51598. IIRC there was also a discussion on the bug tracker a long time ago, but I cannot find it.
Better suggestions for the method name are welcome.
We could implement the copying in the opposite direction:src.copy_into(dst, ...) instead ofdst.copy_replace(src, ...), it could be simpler with choosing the right name, but this is less future proof. What if tomorrow Tk allows to copy from bitmap images (currently it is forbidden) or from other sources? We could not use it in Python until implement a new method of BitmapImage.