/*! * * IPython notebook * */ /* CSS font colors for translated ANSI colors. */ .ansibold { font-weight: bold; } /* use dark versions for foreground, to improve visibility */ .ansiblack { color: black; } .ansired { color: darkred; } .ansigreen { color: darkgreen; } .ansiyellow { color: #c4a000; } .ansiblue { color: darkblue; } .ansipurple { color: darkviolet; } .ansicyan { color: steelblue; } .ansigray { color: gray; } /* and light for background, for the same reason */ .ansibgblack { background-color: black; } .ansibgred { background-color: red; } .ansibggreen { background-color: green; } .ansibgyellow { background-color: yellow; } .ansibgblue { background-color: blue; } .ansibgpurple { background-color: magenta; } .ansibgcyan { background-color: cyan; } .ansibggray { background-color: gray; } div.cell { /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; border-radius: 2px; box-sizing: border-box; -moz-box-sizing: border-box; -webkit-box-sizing: border-box; border-width: 1px; border-style: solid; border-color: transparent; width: 100%; padding: 5px; /* This acts as a spacer between cells, that is outside the border */ margin: 0px; outline: none; border-left-width: 1px; padding-left: 5px; background: linear-gradient(to right, transparent -40px, transparent 1px, transparent 1px, transparent 100%); } div.cell.jupyter-soft-selected { border-left-color: #90CAF9; border-left-color: #E3F2FD; border-left-width: 1px; padding-left: 5px; border-right-color: #E3F2FD; border-right-width: 1px; background: #E3F2FD; } @media print { div.cell.jupyter-soft-selected { border-color: transparent; } } div.cell.selected { border-color: #ababab; border-left-width: 0px; padding-left: 6px; background: linear-gradient(to right, #42A5F5 -40px, #42A5F5 5px, transparent 5px, transparent 100%); } @media print { div.cell.selected { border-color: transparent; } } div.cell.selected.jupyter-soft-selected { border-left-width: 0; padding-left: 6px; background: linear-gradient(to right, #42A5F5 -40px, #42A5F5 7px, #E3F2FD 7px, #E3F2FD 100%); } .edit_mode div.cell.selected { border-color: #66BB6A; border-left-width: 0px; padding-left: 6px; background: linear-gradient(to right, #66BB6A -40px, #66BB6A 5px, transparent 5px, transparent 100%); } @media print { .edit_mode div.cell.selected { border-color: transparent; } } .prompt { /* This needs to be wide enough for 3 digit prompt numbers: In[100]: */ min-width: 14ex; /* This padding is tuned to match the padding on the CodeMirror editor. */ padding: 0.4em; margin: 0px; font-family: monospace; text-align: right; /* This has to match that of the the CodeMirror class line-height below */ line-height: 1.21429em; /* Don't highlight prompt number selection */ -webkit-touch-callout: none; -webkit-user-select: none; -khtml-user-select: none; -moz-user-select: none; -ms-user-select: none; user-select: none; /* Use default cursor */ cursor: default; } @media (max-width: 540px) { .prompt { text-align: left; } } div.inner_cell { min-width: 0; /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; /* Old browsers */ -webkit-box-flex: 1; -moz-box-flex: 1; box-flex: 1; /* Modern browsers */ flex: 1; } /* input_area and input_prompt must match in top border and margin for alignment */ div.input_area { border: 1px solid #cfcfcf; border-radius: 2px; background: #f7f7f7; line-height: 1.21429em; } /* This is needed so that empty prompt areas can collapse to zero height when there is no content in the output_subarea and the prompt. The main purpose of this is to make sure that empty JavaScript output_subareas have no height. */ div.prompt:empty { padding-top: 0; padding-bottom: 0; } div.unrecognized_cell { padding: 5px 5px 5px 0px; /* Old browsers */ display: -webkit-box; -webkit-box-orient: horizontal; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: horizontal; -moz-box-align: stretch; display: box; box-orient: horizontal; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: row; align-items: stretch; } div.unrecognized_cell .inner_cell { border-radius: 2px; padding: 5px; font-weight: bold; color: red; border: 1px solid #cfcfcf; background: #eaeaea; } div.unrecognized_cell .inner_cell a { color: inherit; text-decoration: none; } div.unrecognized_cell .inner_cell a:hover { color: inherit; text-decoration: none; } @media (max-width: 540px) { div.unrecognized_cell > div.prompt { display: none; } } div.code_cell { /* avoid page breaking on code cells when printing */ } @media print { div.code_cell { page-break-inside: avoid; } } /* any special styling for code cells that are currently running goes here */ div.input { page-break-inside: avoid; /* Old browsers */ display: -webkit-box; -webkit-box-orient: horizontal; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: horizontal; -moz-box-align: stretch; display: box; box-orient: horizontal; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: row; align-items: stretch; } @media (max-width: 540px) { div.input { /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; } } /* input_area and input_prompt must match in top border and margin for alignment */ div.input_prompt { color: #303F9F; border-top: 1px solid transparent; } div.input_area > div.highlight { margin: 0.4em; border: none; padding: 0px; background-color: transparent; } div.input_area > div.highlight > pre { margin: 0px; border: none; padding: 0px; background-color: transparent; } /* The following gets added to the if it is detected that the user has a * monospace font with inconsistent normal/bold/italic height. See * notebookmain.js. Such fonts will have keywords vertically offset with * respect to the rest of the text. The user should select a better font. * See: http://bit.ly/2rp8cju * * .CodeMirror span { * vertical-align: bottom; * } */ .CodeMirror { line-height: 1.21429em; /* Changed from 1em to our global default */ font-size: 14px; height: auto; /* Changed to auto to autogrow */ background: none; /* Changed from white to allow our bg to show through */ } .CodeMirror-scroll { /* The CodeMirror docs are a bit fuzzy on if overflow-y should be hidden or visible.*/ /* We have found that if it is visible, vertical scrollbars appear with font size changes.*/ overflow-y: hidden; overflow-x: auto; } .CodeMirror-lines { /* In CM2, this used to be 0.4em, but in CM3 it went to 4px. We need the em value because */ /* we have set a different line-height and want this to scale with that. */ padding: 0.4em; } .CodeMirror-linenumber { padding: 0 8px 0 4px; } .CodeMirror-gutters { border-bottom-left-radius: 2px; border-top-left-radius: 2px; } .CodeMirror pre { /* In CM3 this went to 4px from 0 in CM2. We need the 0 value because of how we size */ /* .CodeMirror-lines */ padding: 0; border: 0; border-radius: 0; } /* Original style from softwaremaniacs.org (c) Ivan Sagalaev Adapted from GitHub theme */ .highlight-base { color: #000; } .highlight-variable { color: #000; } .highlight-variable-2 { color: #1a1a1a; } .highlight-variable-3 { color: #333333; } .highlight-string { color: #BA2121; } .highlight-comment { color: #408080; font-style: italic; } .highlight-number { color: #080; } .highlight-atom { color: #88F; } .highlight-keyword { color: #008000; font-weight: bold; } .highlight-builtin { color: #008000; } .highlight-error { color: #f00; } .highlight-operator { color: #AA22FF; font-weight: bold; } .highlight-meta { color: #AA22FF; } /* previously not defined, copying from default codemirror */ .highlight-def { color: #00f; } .highlight-string-2 { color: #f50; } .highlight-qualifier { color: #555; } .highlight-bracket { color: #997; } .highlight-tag { color: #170; } .highlight-attribute { color: #00c; } .highlight-header { color: blue; } .highlight-quote { color: #090; } .highlight-link { color: #00c; } /* apply the same style to codemirror */ .cm-s-ipython span.cm-keyword { color: #008000; font-weight: bold; } .cm-s-ipython span.cm-atom { color: #88F; } .cm-s-ipython span.cm-number { color: #080; } .cm-s-ipython span.cm-def { color: #00f; } .cm-s-ipython span.cm-variable { color: #000; } .cm-s-ipython span.cm-operator { color: #AA22FF; font-weight: bold; } .cm-s-ipython span.cm-variable-2 { color: #1a1a1a; } .cm-s-ipython span.cm-variable-3 { color: #333333; } .cm-s-ipython span.cm-comment { color: #408080; font-style: italic; } .cm-s-ipython span.cm-string { color: #BA2121; } .cm-s-ipython span.cm-string-2 { color: #f50; } .cm-s-ipython span.cm-meta { color: #AA22FF; } .cm-s-ipython span.cm-qualifier { color: #555; } .cm-s-ipython span.cm-builtin { color: #008000; } .cm-s-ipython span.cm-bracket { color: #997; } .cm-s-ipython span.cm-tag { color: #170; } .cm-s-ipython span.cm-attribute { color: #00c; } .cm-s-ipython span.cm-header { color: blue; } .cm-s-ipython span.cm-quote { color: #090; } .cm-s-ipython span.cm-link { color: #00c; } .cm-s-ipython span.cm-error { color: #f00; } .cm-s-ipython span.cm-tab { background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAMCAYAAAAkuj5RAAAAAXNSR0IArs4c6QAAAGFJREFUSMft1LsRQFAQheHPowAKoACx3IgEKtaEHujDjORSgWTH/ZOdnZOcM/sgk/kFFWY0qV8foQwS4MKBCS3qR6ixBJvElOobYAtivseIE120FaowJPN75GMu8j/LfMwNjh4HUpwg4LUAAAAASUVORK5CYII=); background-position: right; background-repeat: no-repeat; } div.output_wrapper { /* this position must be relative to enable descendents to be absolute within it */ position: relative; /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; z-index: 1; } /* class for the output area when it should be height-limited */ div.output_scroll { /* ideally, this would be max-height, but FF barfs all over that */ height: 24em; /* FF needs this *and the wrapper* to specify full width, or it will shrinkwrap */ width: 100%; overflow: auto; border-radius: 2px; -webkit-box-shadow: inset 0 2px 8px rgba(0, 0, 0, 0.8); box-shadow: inset 0 2px 8px rgba(0, 0, 0, 0.8); display: block; } /* output div while it is collapsed */ div.output_collapsed { margin: 0px; padding: 0px; /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; } div.out_prompt_overlay { height: 100%; padding: 0px 0.4em; position: absolute; border-radius: 2px; } div.out_prompt_overlay:hover { /* use inner shadow to get border that is computed the same on WebKit/FF */ -webkit-box-shadow: inset 0 0 1px #000; box-shadow: inset 0 0 1px #000; background: rgba(240, 240, 240, 0.5); } div.output_prompt { color: #D84315; } /* This class is the outer container of all output sections. */ div.output_area { padding: 0px; page-break-inside: avoid; /* Old browsers */ display: -webkit-box; -webkit-box-orient: horizontal; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: horizontal; -moz-box-align: stretch; display: box; box-orient: horizontal; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: row; align-items: stretch; } div.output_area .MathJax_Display { text-align: left !important; } div.output_area div.output_area div.output_area img, div.output_area svg { max-width: 100%; height: auto; } div.output_area img.unconfined, div.output_area svg.unconfined { max-width: none; } /* This is needed to protect the pre formating from global settings such as that of bootstrap */ .output { /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; } @media (max-width: 540px) { div.output_area { /* Old browsers */ display: -webkit-box; -webkit-box-orient: vertical; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: vertical; -moz-box-align: stretch; display: box; box-orient: vertical; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: column; align-items: stretch; } } div.output_area pre { margin: 0; padding: 0; border: 0; vertical-align: baseline; color: black; background-color: transparent; border-radius: 0; } /* This class is for the output subarea inside the output_area and after the prompt div. */ div.output_subarea { overflow-x: auto; padding: 0.4em; /* Old browsers */ -webkit-box-flex: 1; -moz-box-flex: 1; box-flex: 1; /* Modern browsers */ flex: 1; max-width: calc(100% - 14ex); } div.output_scroll div.output_subarea { overflow-x: visible; } /* The rest of the output_* classes are for special styling of the different output types */ /* all text output has this class: */ div.output_text { text-align: left; color: #000; /* This has to match that of the the CodeMirror class line-height below */ line-height: 1.21429em; } /* stdout/stderr are 'text' as well as 'stream', but execute_result/error are *not* streams */ div.output_stderr { background: #fdd; /* very light red background for stderr */ } div.output_latex { text-align: left; } /* Empty output_javascript divs should have no height */ div.output_javascript:empty { padding: 0; } .js-error { color: darkred; } /* raw_input styles */ div.raw_input_container { line-height: 1.21429em; padding-top: 5px; } pre.raw_input_prompt { /* nothing needed here. */ } input.raw_input { font-family: monospace; font-size: inherit; color: inherit; width: auto; /* make sure input baseline aligns with prompt */ vertical-align: baseline; /* padding + margin = 0.5em between prompt and cursor */ padding: 0em 0.25em; margin: 0em 0.25em; } input.raw_input:focus { box-shadow: none; } p.p-space { margin-bottom: 10px; } div.output_unrecognized { padding: 5px; font-weight: bold; color: red; } div.output_unrecognized a { color: inherit; text-decoration: none; } div.output_unrecognized a:hover { color: inherit; text-decoration: none; } .rendered_html { color: #000; /* any extras will just be numbers: */ } .rendered_html :link { text-decoration: underline; } .rendered_html :visited { text-decoration: underline; } .rendered_html h1:first-child { margin-top: 0.538em; } .rendered_html h2:first-child { margin-top: 0.636em; } .rendered_html h3:first-child { margin-top: 0.777em; } .rendered_html h4:first-child { margin-top: 1em; } .rendered_html h5:first-child { margin-top: 1em; } .rendered_html h6:first-child { margin-top: 1em; } .rendered_html * + ul { margin-top: 1em; } .rendered_html * + ol { margin-top: 1em; } .rendered_html pre, .rendered_html tr, .rendered_html th, .rendered_html td, .rendered_html * + table { margin-top: 1em; } .rendered_html * + p { margin-top: 1em; } .rendered_html * + img { margin-top: 1em; } .rendered_html img, .rendered_html img.unconfined, div.text_cell { /* Old browsers */ display: -webkit-box; -webkit-box-orient: horizontal; -webkit-box-align: stretch; display: -moz-box; -moz-box-orient: horizontal; -moz-box-align: stretch; display: box; box-orient: horizontal; box-align: stretch; /* Modern browsers */ display: flex; flex-direction: row; align-items: stretch; } @media (max-width: 540px) { div.text_cell > div.prompt { display: none; } } div.text_cell_render { /*font-family: "Helvetica Neue", Arial, Helvetica, Geneva, sans-serif;*/ outline: none; resize: none; width: inherit; border-style: none; padding: 0.5em 0.5em 0.5em 0.4em; color: #000; box-sizing: border-box; -moz-box-sizing: border-box; -webkit-box-sizing: border-box; } a.anchor-link:link { text-decoration: none; padding: 0px 20px; visibility: hidden; } h1:hover .anchor-link, h2:hover .anchor-link, h3:hover .anchor-link, h4:hover .anchor-link, h5:hover .anchor-link, h6:hover .anchor-link { visibility: visible; } .text_cell.rendered .input_area { display: none; } .text_cell.rendered .text_cell.unrendered .text_cell_render { display: none; } .cm-header-1, .cm-header-2, .cm-header-3, .cm-header-4, .cm-header-5, .cm-header-6 { font-weight: bold; font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; } .cm-header-1 { font-size: 185.7%; } .cm-header-2 { font-size: 157.1%; } .cm-header-3 { font-size: 128.6%; } .cm-header-4 { font-size: 110%; } .cm-header-5 { font-size: 100%; font-style: italic; } .cm-header-6 { font-size: 100%; font-style: italic; } .highlight .hll { background-color: #ffffcc } .highlight { background: #f8f8f8; } .highlight .c { color: #408080; font-style: italic } /* Comment */ .highlight .err { border: 1px solid #FF0000 } /* Error */ .highlight .k { color: #008000; font-weight: bold } /* Keyword */ .highlight .o { color: #666666 } /* Operator */ .highlight .ch { color: #408080; font-style: italic } /* Comment.Hashbang */ .highlight .cm { color: #408080; font-style: italic } /* Comment.Multiline */ .highlight .cp { color: #BC7A00 } /* Comment.Preproc */ .highlight .cpf { color: #408080; font-style: italic } /* Comment.PreprocFile */ .highlight .c1 { color: #408080; font-style: italic } /* Comment.Single */ .highlight .cs { color: #408080; font-style: italic } /* Comment.Special */ .highlight .gd { color: #A00000 } /* Generic.Deleted */ .highlight .ge { font-style: italic } /* Generic.Emph */ .highlight .gr { color: #FF0000 } /* Generic.Error */ .highlight .gh { color: #000080; font-weight: bold } /* Generic.Heading */ .highlight .gi { color: #00A000 } /* Generic.Inserted */ .highlight .go { color: #888888 } /* Generic.Output */ .highlight .gp { color: #000080; font-weight: bold } /* Generic.Prompt */ .highlight .gs { font-weight: bold } /* Generic.Strong */ .highlight .gu { color: #800080; font-weight: bold } /* Generic.Subheading */ .highlight .gt { color: #0044DD } /* Generic.Traceback */ .highlight .kc { color: #008000; font-weight: bold } /* Keyword.Constant */ .highlight .kd { color: #008000; font-weight: bold } /* Keyword.Declaration */ .highlight .kn { color: #008000; font-weight: bold } /* Keyword.Namespace */ .highlight .kp { color: #008000 } /* Keyword.Pseudo */ .highlight .kr { color: #008000; font-weight: bold } /* Keyword.Reserved */ .highlight .kt { color: #B00040 } /* Keyword.Type */ .highlight .m { color: #666666 } /* Literal.Number */ .highlight .s { color: #BA2121 } /* Literal.String */ .highlight .na { color: #7D9029 } /* Name.Attribute */ .highlight .nb { color: #008000 } /* Name.Builtin */ .highlight .nc { color: #0000FF; font-weight: bold } /* Name.Class */ .highlight .no { color: #880000 } /* Name.Constant */ .highlight .nd { color: #AA22FF } /* Name.Decorator */ .highlight .ni { color: #999999; font-weight: bold } /* Name.Entity */ .highlight .ne { color: #D2413A; font-weight: bold } /* Name.Exception */ .highlight .nf { color: #0000FF } /* Name.Function */ .highlight .nl { color: #A0A000 } /* Name.Label */ .highlight .nn { color: #0000FF; font-weight: bold } /* Name.Namespace */ .highlight .nt { color: #008000; font-weight: bold } /* Name.Tag */ .highlight .nv { color: #19177C } /* Name.Variable */ .highlight .ow { color: #AA22FF; font-weight: bold } /* Operator.Word */ .highlight .w { color: #bbbbbb } /* Text.Whitespace */ .highlight .mb { color: #666666 } /* Literal.Number.Bin */ .highlight .mf { color: #666666 } /* Literal.Number.Float */ .highlight .mh { color: #666666 } /* Literal.Number.Hex */ .highlight .mi { color: #666666 } /* Literal.Number.Integer */ .highlight .mo { color: #666666 } /* Literal.Number.Oct */ .highlight .sa { color: #BA2121 } /* Literal.String.Affix */ .highlight .sb { color: #BA2121 } /* Literal.String.Backtick */ .highlight .sc { color: #BA2121 } /* Literal.String.Char */ .highlight .dl { color: #BA2121 } /* Literal.String.Delimiter */ .highlight .sd { color: #BA2121; 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} .ansi-black-bg { background-color: #3E424D; } .ansi-black-intense-fg { color: #282C36; } .ansi-black-intense-bg { background-color: #282C36; } .ansi-red-fg { color: #E75C58; } .ansi-red-bg { background-color: #E75C58; } .ansi-red-intense-fg { color: #B22B31; } .ansi-red-intense-bg { background-color: #B22B31; } .ansi-green-fg { color: #00A250; } .ansi-green-bg { background-color: #00A250; } .ansi-green-intense-fg { color: #007427; } .ansi-green-intense-bg { background-color: #007427; } .ansi-yellow-fg { color: #DDB62B; } .ansi-yellow-bg { background-color: #DDB62B; } .ansi-yellow-intense-fg { color: #B27D12; } .ansi-yellow-intense-bg { background-color: #B27D12; } .ansi-blue-fg { color: #208FFB; } .ansi-blue-bg { background-color: #208FFB; } .ansi-blue-intense-fg { color: #0065CA; } .ansi-blue-intense-bg { background-color: #0065CA; } .ansi-magenta-fg { color: #D160C4; } .ansi-magenta-bg { background-color: #D160C4; } .ansi-magenta-intense-fg { color: #A03196; } .ansi-magenta-intense-bg { background-color: #A03196; } .ansi-cyan-fg { color: #60C6C8; } .ansi-cyan-bg { background-color: #60C6C8; } .ansi-cyan-intense-fg { color: #258F8F; } .ansi-cyan-intense-bg { background-color: #258F8F; } .ansi-white-fg { color: #C5C1B4; } .ansi-white-bg { background-color: #C5C1B4; } .ansi-white-intense-fg { color: #A1A6B2; } .ansi-white-intense-bg { background-color: #A1A6B2; } .ansi-bold { font-weight: bold; }
Pillow or PIL¶
The Python Image Library (PIL), although not in the standard library, has been Python’s best-known 2-D image processing library. It predated installers such as pip, so a “friendly fork” called Pillow was created. Although the package is called Pillow, you import it as PIL to make it compatible with the older PIL.
Pillow’s documentation is good, check it out here: https://pillow.readthedocs.io/en/stable/
Set-up and install¶
As usual, a virtualenv is created and activated to do our work in.
Pillow can be installed on most platforms and has been tested for the latest Python version (3.7) across the most commonly used platforms. Simply install Pillow with pip:
code
(venv) $ pip install pillow
Let's begin...¶
Let's cover off some basic usage of Pillow; opening Images, resizing and saving images. If you want to follow along, find an image that you want to use and keep it handy in the same working directory of your program.py.
1) Opening (and saving) images¶
It's not unreasonable to have expected that to 'open' on your screen, but that's not what is meant here. You can test if the opening of the image in Python was successful by ensuring it returned an image object:
<class 'PIL.JpegImagePlugin.JpegImageFile'>
Instead, to open, or show, the image on your screen use:
This is the image I am using for this work (it could be the PyBites corporate aircraft?):
Now we have opened the image in Python, let's inspect its image details from the object attributes:
Ok, let's save the image as something else, while also changing the file format from a JPEG to a PNG format:
You should end up with two image files in your working directory: 'original.jpg' and 'new_image.png'.
2) Resizing images¶
Here's where the fun really starts! Of course, it's possible to resize images using Pillow.
The previous image size was determined to be 6000 pixels x 4000 pixels. Let's change that to make the new_image.png smaller. Our watermarking will probably need to be smaller than the image to be watermarked.
To resize an image, we can pass a 2 integer tuple describing width and height to resize().
Let's look at our new image 'new_image_400x400.jpg'
This is what it looks like. Does it look right to you?
The thing to beware of using the resize() function is that is doesn't protect your aspect ratio. It's also therefore possible to blow out the image by making it bigger than the original and lose definition causing it to look a bit fuzzy.
Fortunately, this is where the thumbnail() function comes in handy!
While we have just shrunk our image, another positive of thumbnail is that it cannot upscale the image above the pixel size of the original - no blow out! I.e. setting a pixel size of 8000 x 8000 pixels results in an image size of 6000 x 4000 pixels as per the original dimensions.
This looks much better:
In parts 1) and 2) we covered off how to open an image in Pillow, and on the screen. Then resize it using either the resize function or the preferred thumbnail function which preserves the image's aspect ratio.
Let's now look at how we can paste an image onto another image.
3) Pasting an image onto another image¶
Pasting an image onto another image using Pillow is straightforward and fundamental to creating a watermarked image. For this part, I'm going to use the original aircraft image, and paste the PyBites logo in the bottom right corner to it.
Quite often your second 'watermark' image will have a solid coloured background to it. That needs to be made transparent so that the 'watermark' background merges into the original image well. I'm using a Mac so I refererred to this Apple support page that showed me how to do this. There are methods easily 'Googled' for Windows using Paint too.
This is the PyBites logo from the #100DaysOfCode course, that I modified with a transparent background using the method described above. 
Let's code!
First we'll open the two images. Then make a copy of the original which we'll modify. Then code where we want the PyBites logo to go on the working image, paste it using the paste() function (easy as that!) and save our work:
Here's the result:
But wait! We're using the Pybites logo with a transparent background, aren't we?
Yes we are, but let's look at the Pillow documentation...
Pasting an RGBA image and also using it as the mask will paste the opaque portion of the image but not its transparent background.
We need to pass in a third argument to the paste() function. This argument is the transparency mask Image object. A mask is an Image object where the alpha value is significant, but its green, red, and blue values are ignored. If a mask is given, paste() updates only the regions indicated by the mask.
So let's modify the paste as below to get a pasted logo with transparent pixels.
This is better! (Although we should have resized perhaps!)
In part 3) we covered how to paste a logo image onto a main image, and introduced how the paste function can also take a transparency mask as an optional argument.
4) A final program to paste multiple images over the original¶
As mentioned, the Pillow documentation is really quite good. Advanced users will want to understand how to add/replace alpha layers, or convert to black & white from RGB colours, and change many other parameters.
I encourage you to read the documentation and have a play!
The following code is a variant of the work above. It pastes multiple copies of the PyBites logo watermark all over the original image. While the PyBites logo is a bit of an excessive watermark it demonstrates that a formatted text, possibly with an accompanying logo, can be splashed all over an image you might want to protect online from being copied. This might prevent the image being copied and claimed as someone else's work, whereas a single watermarked image could be cropped out of the original picture.
This results in the following output:
A few evenings play with Pillow increased my knowledge of how to manipulate images in Python with ease. However, my wife opted to use a $1.69 app on her phone to apply a watermark wherever on a photo she might have just taken. It suits her workflow, and I don't have to support it :) But she did later say she wanted a website... "I can do that in Python using Flask!", I said.
Thanks to Bob Belderbos for the inspiration to write this up.
Keep Calm and Code in Python!
-- Anthony
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