Crop image bigger than page from top left to bottom right

Question

I have a small problem when including an image bigger than an A4 page. Normally, I would use this code, but with this I am able to crop it using the bounding box, from 0, 0 to 500,700:

%%image start
\begin{figure}[h!]
      \caption{\url{http://www.url.com/.htm}
  \newline
  Text
  \newline
}
  \centering
   % cropped at 500 x 700
    \includegraphics[bb= 0 0 500 700 ,clip]{images/001.png}
\end{figure}
%%image end

The thing is that my image is bigger than the page (but every image has a different size), so I'd like to crop it from the upper left to the bottom right, cutting the lower part, let's say having an image tall 700. Is it possible to do that using the bounding box or some other thing?

Answer 1

The only idea which came to my mind was to store the graphic in a box, which allows us to query tex about its height (\ht), and use that value as the y-coordinate of a corner of the bounding box, then substract the desired height from that value, and use the result as the y-coordinate of the other corner.

I wrote a macro which does those calculations. Here is a MWE:

\documentclass{article}
\usepackage{mwe}  % For the sample images
\usepackage{graphicx}
\newcommand{\includeclippedgraphics}[3]{%
  % #1 = width
  % #2 = height
  % #3 = graphics file
  \setbox0=\hbox{\includegraphics{#3}}%
  \dimen1=\ht0\advance\dimen1 by -#2bp%
  \includegraphics[clip, viewport=0 \dimen1 #1 \ht0]{#3}%
}
\begin{document}
  % Original image
  \includegraphics{example-image}  
  \vskip 5mm
  % Standard crop (from bottom left corner)
  \includegraphics[clip, bb=0 0 160 120]{example-image}      
  \vskip 5mm
  % New crop (from upper left corner)
  \includeclippedgraphics{160}{120}{example-image}
\end{document}

Result:

Update

I introduced a variation, in which the first argument of the macro (the required width for the image) is optional. If omitted, the native width is used, so you specify only the required vertical size and the bottom of the image gets cropped.

\documentclass{article}
\usepackage{mwe}  % For the sample images
\usepackage{graphicx}
\usepackage[margin=5mm]{geometry}
\newcommand{\includeclippedgraphics}[3][0]{%
  % #1 = width (optional)
  % #2 = height
  % #3 = graphics file
  \setbox0=\hbox{\includegraphics{#3}}%
  \dimen1=\ht0\advance\dimen1 by -#2bp%
  \ifnum#1=0\dimen2=\wd0\else\dimen2=#1bp\fi
  \includegraphics[clip, viewport=0 \dimen1 \dimen2 \ht0]{#3}%
}
\begin{document}
  % Original image
  \includegraphics{example-image}
  \vskip 5mm
  % Standard crop (from bottom left corner)
  \includegraphics[clip, bb=0 0 160 120]{example-image}
  \vskip 5mm
  % New crop (from upper left corner) with optional width set to 160
  \includeclippedgraphics[160]{120}{example-image}
  \vskip 5mm
  % New crop (from upper left corner) with optional width omitted
  \includeclippedgraphics{120}{example-image}
\end{document}

And the result: